Annales Geophysicae最新文献

{"title":"Impulse-driven oscillations of the near-Earth's magnetosphere","authors":"H. Sato, H. Pécseli, J. Trulsen, P. Sandholt, C. Farrugia","doi":"10.5194/angeo-40-641-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-641-2022","url":null,"abstract":"Abstract. It is argued that a simple model based on magnetic image arguments suffices to give a convincing insight into both the basic static as well as some transient dynamic properties of the near-Earth's magnetosphere, particularly accounting for damped oscillations being excited in response to impulsive perturbations. The parameter variations of the frequency are given. Qualitative results can also be obtained for heating due to the compression of the radiation belts. The properties of this simple dynamic model for the solar wind–magnetosphere interaction\u0000are discussed and compared to observations. In spite of its simplicity,\u0000the model gives convincing results concerning the magnitudes of the near-Earth's magnetic and electric fields. The database contains\u0000ground-based results for magnetic field variation in response to shocks in the solar wind. Here, the observations also include data from the two Van Allen satellites.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"34 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79758772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-instrument observations of polar cap patches and traveling ionospheric disturbances generated by solar wind Alfvén waves coupling to the dayside magnetosphere","authors":"P. Prikryl, Robert G. Gillies, D. Themens, J. Weygand, E. Thomas, S. Chakraborty","doi":"10.5194/angeo-40-619-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-619-2022","url":null,"abstract":"Abstract. During minor to moderate geomagnetic storms, caused by corotating\u0000interaction regions (CIRs) at the leading edge of high-speed streams (HSSs), solar wind\u0000Alfvén waves modulated the magnetic reconnection at the dayside\u0000magnetopause. The Resolute Bay Incoherent Scatter Radars (RISR-C and\u0000RISR-N), measuring plasma parameters in the cusp and polar cap, observed\u0000ionospheric signatures of flux transfer events (FTEs) that resulted in the\u0000formation of polar cap patches. The patches were observed as they moved over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN)\u0000ionosondes and GPS receivers. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including the auroral electrojets. The horizontal equivalent ionospheric currents (EICs) are estimated from ground-based magnetometer data using an inversion technique. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves, causing traveling\u0000ionospheric disturbances (TIDs) that propagated equatorward. The TIDs were\u0000observed in the SuperDual Auroral Radar Network (SuperDARN) high-frequency (HF) radar ground\u0000scatter and the detrended total electron content (TEC) measured by globally\u0000distributed Global Navigation Satellite System (GNSS) receivers.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"14 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74322581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic local time (MLT) dependence of auroral peak emission height and morphology","authors":"N. Partamies, D. Whiter, K. Kauristie, S. Massetti","doi":"10.5194/angeo-40-605-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-605-2022","url":null,"abstract":"Abstract. We investigate the bulk behaviour of auroral structures and peak emission height as a function of magnetic local time (MLT). These data are collected from the Fennoscandian Lapland and Svalbard latitudes from seven identical auroral all-sky cameras (ASC) over about one solar cycle. The analysis focusses on green auroral emission, which is where the morphology is most clearly visible and the number of images is the highest. The typical peak emission height of the green and blue aurora varies from 110 km on the nightside to about 118 km in the morning MLT over the Lapland region. It stays systematically higher (at 118–120 km) at high latitudes (Svalbard) during the nighttime and reaches 140 km at around magnetic noon. During high solar wind speed (above 500 km s−1), nightside emission heights appear about 5 km lower than during slow solar wind speed (below 400 km s−1). The sign of the interplanetary magnetic field (IMF) has nearly no effect on the emission heights in the night sector, but the northward IMF causes lower emission heights at dawn over Lapland and during the noon hours over Svalbard. While the former is interpreted as a change in the particle population within the field-of-view (FoV), the latter is rather due to the movement of the cusp location due to the IMF orientation. The morning sector heights also show a pronounced difference when previously detected pulsating aurora (PsA) events have been excluded/included in the dataset, suggesting that this type of aurora is a dominant phenomenon in the morning and an important dissipation mechanism. An increase of complex auroral structures in the midnight hours agrees with the average substorm occurrence. This increase is amplified during stronger solar wind driving and during higher geomagnetic activity (as measured by auroral electrojet index, AL). During high solar wind speed, the high latitude auroral evolution shows particularly complex morphology, which is not limited to the nightside but rather only excludes the magnetic noon hours. An increase in the geomagnetic activity further enhances the structural complexity of the aurora in the morning sector.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"4 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73453670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionospheric effects of the 5–6 January 2019 eclipse over the People's Republic of China: results from oblique sounding","authors":"L. Chernogor, K. Garmash, Q. Guo, V. Rozumenko, Yu. Zheng","doi":"10.5194/angeo-40-585-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-585-2022","url":null,"abstract":"Abstract. This paper deals with the variations in the Doppler spectra and in the relative amplitudes of the signals observed at oblique\u0000incidence over the People's Republic of China (PRC) during the partial solar eclipse of 5–6 January 2019 and on reference days. The observations were made using the multifrequency multipath radio system for sounding the\u0000ionosphere at oblique incidence. The receiver system is located at the\u0000Harbin Engineering University, PRC, and 14 HF broadcasting station\u0000transmitters are used for taking measurements along the following radio-wave propagation paths: Lintong/Pucheng to Harbin, Hwaseong to Harbin, Chiba/Nagara to Harbin, Hailar/Nanmen to Harbin, Beijing to Harbin (three paths), Goyang to Harbin, Ulaanbaatar/Khonkhor to Harbin, Yakutsk to Harbin (two paths), Shijiazhuang to Harbin, Hohhot to Harbin, and Yamata to Harbin. The specific feature of this partial solar eclipse was that it occurred during the local morning with a geomagnetic disturbance (Kp ≈ 3−) in the background. The response of the ionosphere to the solar eclipse has been inferred from temporal variations in the Doppler spectra, the Doppler shift, and the signal relative amplitude. The partial solar eclipse was found to be associated with broadening of the Doppler spectrum, up\u0000to ± 1.5 Hz, alternating sign Doppler-shift variations, up to ± 0.5 Hz, in the main ray, and quasi-periodic Doppler-shift changes. The relative amplitude of electron density disturbances in the 15 min period of atmospheric gravity wave field and in the 4–5 min period of infrasound wave field is estimated to be 1.6 %–2.4 % and 0.2 %–0.3 %, respectively. The estimates of a maximum decrease in the electron density are in agreement with the observations.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"72 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76462549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mid-latitude neutral wind responses to sub-auroral polarization streams","authors":"D. Billett, K. McWilliams, R. Kerr, J. Makela, Alex T. Chariter, J. Ruohoniemi, S. Kapali, M. Migliozzi, J. Riccobono","doi":"10.5194/angeo-40-571-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-571-2022","url":null,"abstract":"Abstract. We investigate the response of the mid-latitude thermospheric neutral winds to a sub-auroral polarization stream (SAPS) event. Using red line (F region) airglow data from two Fabry–Pérot interferometers (FPIs), and F-region ionospheric flow velocities from four Super Dual Auroral Radar Network (SuperDARN) radars, the drivers behind changes seen in the neutral winds are explored within the context of the larger SAPS structure. Different, although strong, neutral wind responses to the SAPS are seen at the two FPI sites, even though they are relatively close geographically. We attribute the wind differences to the varying balance of pressure gradient, ion drag, and Coriolis forces, which ultimately depend on proximity to the SAPS. At the FPI site equatorward of the SAPS, pressure gradient and Coriolis forces drive the winds equatorward and then westward. At the FPI site co-located with the SAPS, the ion drag is strong and results in the winds surging westward before turning eastward when becoming influenced by dawnside sunward plasma convection drifts.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"1 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90068706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temporal and altitudinal variability of the spread F observed by the VHF radar over Christmas Island","authors":"Ricardo Yvan de La Cruz Cueva, Eurico Rodrigues de Paula, Acácio Cunha Neto","doi":"10.5194/angeo-40-563-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-563-2022","url":null,"abstract":"Abstract. The goal of this work is to study the time and altitude\u0000echo characteristics under different solar and seasonality conditions using the VHF radar range–time–intensity (RTI) images. The occurrence of equatorial spread F depends on the existence of conditions that can seed the Rayleigh–Taylor instability, and these conditions can change with solar flux, seasonality,\u0000longitude distributions, and day-to-day variability. So, the equatorial\u0000spread F is observed as its time and altitude occurrence. The VHF radar of\u0000Christmas Island (2.0∘ N, 157.4∘ W, 2.9∘ N dip\u0000latitude) has been operational in the equatorial region for some time,\u0000allowing long-term observations. The occurrence of echoes during solar\u0000minimum conditions is observed throughout the night since the post-reversal westward electric field is weaker than the solar maximum and the\u0000possibilities of the vertical plasma drift becoming positive are larger. On the other hand, echoes during solar maximum will be controlled by dynamics near the time of the pre-reversal peak (PRE). Our results indicate that the\u0000peak time occurrence of echoes along this period shows a well-defined\u0000pattern, with echoes distributed as closer to local sunset during solar\u0000maximum and around/closer to midnight during solar minimum conditions; meanwhile, the peak altitude occurrence of echoes shows a slightly regular\u0000pattern with higher-altitude occurrences during solar maxima and lower altitudes during solar minimum conditions.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"30 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79975683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple conjugate observations of magnetospheric fast flow bursts using THEMIS observations","authors":"Homayon Aryan, J. Bortnik, Jinxing Li, J. Weygand, X. Chu, V. Angelopoulos","doi":"10.5194/angeo-40-531-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-531-2022","url":null,"abstract":"Abstract. Magnetotail earthward fast flow bursts can transport most magnetic flux and energy into the inner magnetosphere. These fast flow bursts\u0000are generally an order of magnitude higher than the typical convection speeds that are azimuthally localised (1–3 RE) and are flanked by\u0000plasma vortices, which map to ionospheric plasma vortices of the same sense of rotation. This study uses a multipoint analysis of conjugate\u0000magnetospheric and ionospheric observations to investigate the magnetospheric and ionospheric responses to fast flow bursts that are associated\u0000with both substorms and pseudobreakups. We study in detail what properties control the differences in the magnetosphere–ionosphere responses between\u0000substorm fast flow bursts and pseudobreakup events, and how these differences lead to different ionospheric responses. The fast flow bursts and\u0000pseudobreakup events were observed by the Time History of Events and Macroscale Interaction during Substorms (THEMIS), while the primary ionospheric\u0000observations were made by all-sky cameras and magnetometer-based equivalent ionospheric currents. These events were selected when the satellites\u0000were at least 6 RE from the Earth in radial distance and a magnetic local time (MLT) region of ± 5 h from local midnight. The\u0000results show that the magnetosphere and ionosphere responses to substorm fast flow bursts are much stronger and more structured compared to\u0000pseudobreakups, which are more likely to be localised, transient and weak in the magnetosphere. The magnetic flux in the tail is much stronger for\u0000strong substorms and much weaker for pseudobreakup events. The Blobe decreases significantly for substorm fast flow bursts compared to\u0000pseudobreakup events. The curvature force density for pseudobreakups are much smaller than substorm fast flow events, indicating that the\u0000pseudobreakups may not be able to penetrate deep into the inner magnetosphere. This association can help us study the properties and activity of the\u0000magnetospheric earthward flow vortices from ground data.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"116 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79507785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Arecibo measurements of D-region electron densities during sunset and sunrise: implications for atmospheric composition","authors":"C. Baumann, A. Kero, S. Raizada, M. Rapp, M. Sulzer, P. Verronen, J. Vierinen","doi":"10.5194/angeo-40-519-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-519-2022","url":null,"abstract":"Abstract. Earth's lower ionosphere is the region where terrestrial weather and space weather come together. Here, between 60 and 100 km altitude,\u0000solar radiation governs the diurnal cycle of the ionized species. This altitude range is also the place where nanometre-sized dust particles,\u0000recondensed from ablated meteoric material, exist and interact with free electrons and ions of the ionosphere. This study reports electron density\u0000measurements from the Arecibo incoherent-scatter radar being performed during sunset and sunrise conditions. An asymmetry of the electron density is\u0000observed, with higher electron density during sunset than during sunrise. This asymmetry extends from solar zenith angles (SZAs) of 80 to\u0000100∘. This D-region asymmetry can be observed between 95 and 75 km altitude. The electron density observations are compared to the\u0000one-dimensional Sodankylä Ion and Neutral Chemistry (SIC) model and a variant of the Whole Atmosphere Community Climate Model incorporating a\u0000subset SIC's ion chemistry (WACCM-D). Both models also show a D-region sunrise–sunset asymmetry. However, WACCM-D compares slightly better to the\u0000observations than SIC, especially during sunset, when the electron density gradually fades away. An investigation of the electron density continuity\u0000equation reveals a higher electron–ion recombination rate than the fading ionization rate during sunset. The recombination reactions are not fast\u0000enough to closely match the fading ionization rate during sunset, resulting in excess electron density. At lower altitudes electron attachment to\u0000neutrals and their detachment from negative ions play a significant role in the asymmetry as well. A comparison of a specific SIC version\u0000incorporating meteoric smoke particles (MSPs) to the observations revealed no sudden changes in electron density as predicted by the model. However,\u0000the expected electron density jump (drop) during sunrise (sunset) occurs at 100∘ SZA when the radar signal is close to the noise floor,\u0000making a clear falsification of MSPs' influence on the D region impossible.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"150B 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73120026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of the equatorial and low-latitude total electron content response to plasma bubbles during solar cycle 24–25 over the Brazilian region using a Disturbance Ionosphere indeX","authors":"G. Picanço, C. Denardini, P. Nogueira, L. Resende, C. S. Carmo, S. S. Chen, P. F. Barbosa-Neto, E. Romero‐Hernández","doi":"10.5194/angeo-40-503-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-503-2022","url":null,"abstract":"Abstract. This work uses the Disturbance Ionosphere indeX (DIX) to evaluate\u0000the ionospheric responses to equatorial plasma bubble (EPB) events from\u00002013 to 2020 over the Brazilian equatorial and low latitudes. We have\u0000compared the DIX variations during EPBs to ionosonde and All-Sky Imager\u0000data, aiming to evaluate the physical characteristics of these events. Our\u0000results show that the DIX was able to detect EPB-related TEC disturbances in terms of their intensity and occurrence times. Thus, the EPB-related DIX\u0000responses agreed with the ionosphere behavior before, during, and after the\u0000studied cases. Finally, we found that the magnitude of those disturbances\u0000followed most of the trends of solar activity, meaning that the EPB-related\u0000total electron content variations tend to be higher (lower) in high (low) solar activity.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"20 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78120234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sounding of sporadic E layers from China Seismo-Electromagnetic Satellite (CSES) radio occultation and comparing with ionosonde measurements","authors":"Chengkun Gan, Jiayu Hu, Xiaomin Luo, Chao Xiong, S. Gu","doi":"10.5194/angeo-40-463-2022","DOIUrl":"https://doi.org/10.5194/angeo-40-463-2022","url":null,"abstract":"Abstract. GNSS radio occultation (RO) plays an important role in\u0000ionospheric electron density inversion and sounding of sporadic E layers. As\u0000China's first electromagnetic satellite, China Seismo-Electromagnetic\u0000Satellite (CSES) has collected the RO data from both GPS and BDS-2\u0000satellites since March 2018. In this study, we extracted the signal-to-noise\u0000ratio (SNR) data of CSES and calculated the standard deviation of normalized\u0000SNR. A new criterion is developed to determine the Es events, that is, when\u0000the mean value of the absolute value of the difference between the\u0000normalized SNR is greater than 3 times the standard deviation. The\u0000statistics show that sporadic E layers have strong seasonal variations with\u0000highest occurrence rates in summer season at middle latitudes. It is also\u0000found that the occurrence height of Es is mainly located at 90–110 km, and\u0000the period 14:00–20:00 LT is the high incidence period of Es. In\u0000addition, the geometric altitudes of a sporadic E layer detected in CSES\u0000radio occultation profiles and the virtual heights of a sporadic E layer\u0000obtained by the Wuhan Zuoling station (ZLT) ionosonde show three different\u0000space-time matching criteria. Our results reveal that there is a good\u0000agreement between both parameters which is reflected in the significant\u0000correlation.\u0000","PeriodicalId":50777,"journal":{"name":"Annales Geophysicae","volume":"1 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84619114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}