Periods Of High Geomagnetic Activity Research Articles

Lightning‐Induced Energetic Electron Precipitation Observed in Long‐Term DEMETER Spacecraft Measurements

AbstractWe analyze low‐altitude DEMETER spacecraft measurements obtained between 2006 and 2010, complemented by WWLLN lightning location data, to investigate the importance of lightning‐generated whistlers for the energetic electron precipitation from the Van Allen radiation belts. We focus, in particular, on the United States region, where a significant seasonal variation in the occurrence of lightning has been observed. We show that both the precipitating electron fluxes and very low frequency wave intensities correlate well with the total lightning occurrence in the region. We further demonstrate that lightning‐induced electron precipitation is more significant during periods of low geomagnetic activity compared to periods of high geomagnetic activity and during the nighttime than during the daytime. The energies of precipitating energetic electrons extend up to about 700 keV, roughly in agreement with the cyclotron resonance theory.

Properties of the Variability of the Maximum Density of the F2-Layer over Almaty at Different Levels of Solar and Geomagnetic Activity

The properties of the variability of the maximum density of the F2-layer Nm at different levels ofsolar and geomagnetic activity have been analyzed based on hourly data of the Almaty station (43.2° N, 104° E)for 1958–1988. The standard deviation σ(x) of the fluctuations of Nm relative to the quiet level(x = (Nm/Nm0 – 1) × 100, %) and the average shift of these fluctuations xave are used to characterize thisvariability. In this path, an empirical model of the F2-layer maximum density Nm0 for low geomagnetic activityhas been created. It has been found that the variability of Nm depends weakly on the level of solar activity.The dependence of the variability of Nm on geomagnetic activity is one of the main ones, along with thedependences of this variability on time of day and season. In general, the variance σ2(x) is smaller for quietconditions than for periods of high geomagnetic activity. However, during periods of high geomagnetic activity,a further increase in geomagnetic activity does not lead to an increase in the variance σ2(x). The saturationin the increase in the variance σ2(x) against the background of a continuing increase in geomagnetic activityand the absence of this saturation for the average shift xave seems to be a stable property of the variability ofthe mid-latitude ionosphere during periods of geomagnetic storms. This conclusion is based on an additionalanalysis of ionospheric variability according to data from the Irkutsk and Yamagawa stations, which arelocated about 10 degrees north and south of Almaty station, respectively.

Effect of geomagnetic activity on investors and managers: evidence from the pricing and timing of disclosure of earnings news

PurposeThis paper's purpose was to examine the impact of geomagnetic activity (GMA) on the timing and valuation of earnings information disclosed by firms every quarter.Design/methodology/approachThe authors start the analyses with a sample of 112,669 client firms from 1989 to 2018. To analyze the impact of GMA on the earnings response coefficient (ERC), the authors use the three-day cumulative abnormal returns and cumulative abnormal returns for the extended post-earnings announcement window [2, 75] as the dependent variables. The authors interact unexpected earnings (UE) with the C9 Index, an index commonly used to measure GMA and study how GMA affects the pricing of new public information. To examine the effect of GMA on the timing of disclosure of earnings news, the authors regress a variant of the GMA index on the propensity to disclose bad earnings news.FindingsThe authors find significantly lower earnings response coefficients during periods of high GMA. This effect is permanent and stock prices do not correctly incorporate the implications of earnings information over time. The authors also show that managerial behavior is affected by GMA as well and the managers are more (less) likely to release bad (good) news during periods of higher activity. Finally, the authors also find that in situations where stakeholders are likely to rely on modern technology that depends minimally on humans, the adverse impact of GMA on the pricing of earnings information is mitigated.Originality/valueThe literature on the effect of GMA on the capital market is very limited and focuses primarily on stock returns, while the behavioral finance literature focuses on circumstances like weather, temperature and sporting outcome to study how the investors' mood affects their capital market behavior. The authors add to both the literature by investigating how GMA influences investors' and managers' behaviors in the capital market.

Diagnosing low earth orbit satellite anomalies using NOAA-15 electron data associated with geomagnetic perturbations

A satellite placed in space is constantly affected by the space environment, resulting in various impacts from temporary faults to permanent failures depending on factors such as satellite orbit, solar and geomagnetic activities, satellite local time, and satellite construction material. Anomaly events commonly occur during periods of high geomagnetic activity that also trigger plasma variation in the low Earth orbit (LEO) environment. In this study, we diagnosed anomalies in LEO satellites using electron data from the Medium Energy Proton and Electron Detector onboard the National Oceanic and Atmospheric Administration (NOAA)-15 satellite. In addition, we analyzed the fluctuation of electron flux in association with geomagnetic disturbances 3 days before and after the anomaly day. We selected 20 LEO anomaly cases registered in the Satellite News Digest database for the years 2000–2008. Satellite local time, an important parameter for anomaly diagnosis, was determined using propagated two-line element data in the SGP4 simplified general perturbation model to calculate the longitude of the ascending node of the satellite through the position and velocity vectors. The results showed that the majority of LEO satellite anomalies are linked to low-energy electron fluxes of 30–100 keV and magnetic perturbations that had a higher correlation coefficient (~ 90%) on the day of the anomaly. The mean local time calculation for the anomaly day with respect to the nighttime migration of energetic electrons revealed that the majority of anomalies (65%) occurred on the night side of Earth during the dusk-to-dawn sector of magnetic local time.

Coronal Mass Ejections in September 2017 from Monitoring of Interplanetary Scintillations with the Large Phased Array of the Lebedev Institute of Physics

Results of monitoring of interplanetary scintillations with the Large Phased Array of the Pushchino Radio AstronomyObservatory at 111 MHz during a period of flare activity of the Sun in the first ten days of September 2017 are presented. Enhancements of scintillations associated with interplanetary coronal mass ejections propagating after limb flares have been recorded. The propagation velocities are estimated to be about 2000 km/s for an ejection on September 7 and about 1000 km/s for an ejection on September 6. It is shown that, during the propagation from the Sun, the lateral part of the ejections decelerates faster than its leading part. Night-time enhancements of second-timescale scintillations during periods of high geomagnetic activity have an ionospheric origin.

Свойства изменчивости концентрации максимума F2-слоя над Иркутском при разных уровнях солнечной и геомагнитной активности

Using hourly data (1958–1992) from Irkutsk ionosonde station, we analyzed properties of variability of the F2-layer maximum density, Nm, under different levels of the solar and geomagnetic activity. The standard deviation s(x) of Nm fluctuations relative to the quiet level (x=(Nm/Nm0–1)·100 %), and the average shift of these fluctuations x-ave were used as characteristics of this variability. For this purpose, the empirical model of the F2-layer maximum density for quiet magnetic conditions, Nm0, was constructed. The Nm variability was found to depend weakly on the solar activity level; in the first approximation, this dependence can be neglected. The Nm variability dependence on geomagnetic activity is among the principal ones, along with the dependences on local time and season. In general, dispersion of Nm fluctuations under quiet conditions is smaller than that during the periods of high geomagnetic activity. During the periods of high geomagnetic activity, however, the dispersion does not increase with the further growth of this activity, while the absolute value of shift x-ave (which is mainly negative under high geomagnetic activity) still increases with growing geomagnetic activity. As a result, if this activity is high enough, the condition |x-ave|>|s(x)| can be fulfilled.

The Heppner‐Maynard Boundary measured by SuperDARN as a proxy for the latitude of the auroral oval

We present a statistical study relating the latitude of the auroral oval measured by the Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) SI‐12 proton auroral camera to that of the Heppner‐Maynard Boundary (HMB) determined from Super Dual Auroral Radar Network (SuperDARN) data during the period 2000–2002. The HMB represents the latitudinal extent of the ionospheric convection pattern. The oval latitude from the proton auroral images is determined using the method of Milan et al. (2009a), which fits a circle centered on a point 2° duskward and 5° antisunward of the magnetic pole. The auroral latitude at midnight is determined for those images where the concurrent SuperDARN northern hemisphere maps contain more than 200 data points such that the HMB is well‐defined. The statistical study comprises over 198,000 two‐minute intervals, and we find that the HMB is located on average 2.2° equatorward of the proton auroral latitude. A superposed epoch analysis of over 2500 substorms suggests that the separation between the HMB and the oval latitude increases slightly during periods of high geomagnetic activity. We suggest that during intervals where there are no auroral images available, the HMB latitude and motion could be used as a proxy for that of the aurora, and therefore provide information about motions of the open/closed field line boundary.

Effects of geomagnetic disturbances in the near Earth’s atmosphere and possible biophysical mechanism of their influence on the human cardiovascular system

We analyze the effect of geomagnetic activity on variations in quasi-static electric field strength and the horizontal geomagnetic field component in the band of periods of tidal and planetary waves. Variations in oscillation intensities and periods in the power spectra of these parameters synchronously with the Kp index are shown. Taking into account the relationship of these parameters with the air pressure, we suggest a possible biophysical mechanism of the relation between the state of the human cardiovascular system and geomagnetic activity by means of resonant interaction with the environment. In periods of high geomagnetic activity, the air pressure and temperature vary due to an increase in atmospheric transparency as a result of the Forbush decrease in the cosmic ray flux rate. It is these variations that directly affect humans.

Will climate change increase ozone depletion from low-energy-electron precipitation?

Abstract. We investigate the effects of a strengthened stratospheric/mesospheric residual circulation on the transport of nitric oxide (NO) produced by energetic particle precipitation. During periods of high geomagnetic activity, energetic electron precipitation (EEP) is responsible for winter time ozone loss in the polar middle atmosphere between 1 and 6 hPa. However, as climate change is expected to increase the strength of the Brewer-Dobson circulation including extratropical downwelling, the enhancements of EEP NOx concentrations are expected to be transported to lower altitudes in extratropical regions, becoming more significant in the ozone budget. Changes in the mesospheric residual circulation are also considered. We use simulations with the chemistry climate model system EMAC to compare present day effects of EEP NOx with expected effects in a climate change scenario for the year 2100. In years of strong geomagnetic activity, similar to that observed in 2003, an additional polar ozone loss of up to 0.4 μmol/mol at 5 hPa is found in the Southern Hemisphere. However, this would be approximately compensated by an ozone enhancement originating from a stronger poleward transport of ozone from lower latitudes caused by a strengthened Brewer-Dobson circulation, as well as by slower photochemical ozone loss reactions in a stratosphere cooled by risen greenhouse gas concentrations. In the Northern Hemisphere the EEP NOx effect appears to lose importance due to the different nature of the climate-change induced circulation changes.

A three-dimensional modelling study of the processes leading to mid latitude nitric oxide increases in the lower thermosphere following periods of high geomagnetic activity

The processes leading to enhancements in mid latitude nitric oxide (NO) densities following geomagnetic storms have been investigated using the University College London (UCL) Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model. A comparison of calculated storm time and quiet time NO densities at 110 km altitude reveals the presence of aurorally produced NO at both high and mid latitudes for several days after subsidence of activity. At 150 km, the NO enhancements are shorter lived and remain for up to approximately 2 days after the storm. By separating the contribution of chemical production and loss, horizontal and vertical advection, and molecular and eddy diffusion in the calculation of NO densities, we show that at 150 km altitude, horizontal transport must be taken into consideration if post-storm mid latitude enhancements are to be reproduced. Chemical production of NO at high latitudes continues for up to 2 days after subsidence of a storm at altitudes of around 150 km. We show that equatorward winds at this altitude are sufficiently strong to transport the aurorally produced NO to mid latitudes. Vertical diffusion transports NO from altitudes of 150 km and above, to lower altitudes where it is longer lived. At 110 km altitude, chemical, diffusive and advective terms must all be included in the calculation of NO density in order to simulate realistic mid latitude enhancements. We propose that it is the combined effects of increased chemical production, downward diffusion from altitudes of 150 km and above, and transport by winds that lead to increases in mid latitude NO density at altitudes of around 110 km. This is the first detailed study of the causes of post-storm mid latitude NO enhancements to use a three-dimensional general circulation model.

Remote sensing of ionospheric disturbances associated with energetic particle precipitation using the South Pole VLF beacon

[1] The Stanford University VLF beacon transmitter located at South Pole operates at 19.4 kHz, transmitting for 1 min intervals every 15 min throughout the day. The beacon serves as a tool to measure changes in the D region ionospheric conductivity owing to energetic particle precipitation and is capable of providing coverage that spans the Antarctic continent. We present VLF beacon signal amplitude and phase data measured at Palmer Station, Antarctica. Diurnal and seasonal variations are discussed first, followed by analysis of data from two periods of high geomagnetic activity, in July 2004 and in May 2005, with a phase advance and an amplitude depression of the beacon signal (as recorded at Palmer) observed for both cases. Data from the MEPED instrument aboard the NOAA-16 and 17 POES satellites show an increase in energetic electron (>100 keV) and proton (>16 MeV) precipitation fluxes coincident with the VLF beacon signal perturbations. The fluxes measured on POES are used as an aide to generate profiles of secondary ionization along the great circle path from South Pole to Palmer. These profiles are then applied to a quantitative model of subionospheric VLF signal propagation to estimate the phase and amplitude variations expected. Results indicate that the observed VLF amplitude and phase data are in reasonable agreement with theoretical calculations in both cases, indicating that the model captures the ionospheric disturbance in effect during both of the disturbed periods.

3-D GCM modelling of thermospheric nitric oxide during the 2003 Halloween storm

Abstract. Numerical modelling of thermospheric temperature changes associated with periods of high geomagnetic activity are often inaccurate due to unrealistic representation of nitric oxide (NO) densities and associated 5.3-μm radiative cooling. In previous modelling studies, simplistic parameterisations of NO density and variability have often been implemented in order to constrain thermospheric temperature predictions and post storm recovery timescales during and following periods of high auroral activity. In this paper we use the University College London (UCL) 3-D Coupled Thermosphere and Middle Atmosphere (CMAT) General Circulation Model to simulate the 11-day period from 23 October to 3 November 2003, during which the Earth experienced some of the largest geomagnetic activity ever recorded; the so called "Halloween storm". This model has recently been updated to include a detailed self consistent calculation of NO production and transport. Temperatures predicted by the model compare well with those observed by the UCL Fabry Perot Interferometer at Kiruna, northern Sweden, when changes in solar and auroral activity are taken into account in the calculation of NO densities. The spatial distribution of predicted temperatures at approximately 250-km altitude is also discussed. Simulated NO densities at approximately 110 km are presented. Large quantities of NO are found to be present at to the equator, one to two days after the most intense period of geomagnetic activity. This is the first 3-D GCM simulation of NO production and transport over the 2003 Halloween storm period.

Three‐dimensional GCM modeling of nitric oxide in the lower thermosphere

The coupled middle atmosphere and thermosphere (CMAT) general circulation model has been used to predict the global distribution of nitric oxide (NO) in the lower thermosphere. This three‐dimensional (3‐D) model incorporates a complex ion and neutral chemical scheme, high‐resolution solar flux data and variable auroral energy inputs. Comparison of simulated NO densities with those observed by the Student Nitric Oxide Explorer (SNOE) show that the CMAT model is able to recreate large‐scale features in the observed NO distribution under differing geophysical conditions. While previous studies have used 1‐D photochemical models to speculate on the latitudinal extent of aurorally produced NO, we have simulated NO production and transport in three dimensions under both geomagnetically stable and disturbed conditions. We have shown that the spatial and temporal distribution of aurorally produced NO is highly variable with location and local time. CMAT simulations suggest that under moderate geomagnetic conditions, the most equatorward geographic latitudes to be influenced by aurorally produced NO are 30°S and 45°N. Under conditions of high geomagnetic activity, aurorally produced NO is present at latitudes poleward of 15°S and 28°N. The asymmetry in latitudinal extent is attributed to the greater offset between geographic and geomagnetic poles in the southern hemisphere. NO density maxima are predicted to occur between 14 and 48 hours after a period of high geomagnetic activity, their spatial and temporal distribution depending on location with respect to the auroral oval and local time at which auroral forcing occurs.

Comparisons between EUV/IMAGE observations and numerical simulations of the plasmapause formation

Abstract. Simulations of plasmapause formation described in Pierrard and Lemaire (2004) predict the shape and equatorial distance of the plasmapause as a function of the geomagnetic activity index Kp. The equatorial positions predicted by this model are compared with the observations of EUV/IMAGE during the geomagnetic storm of 24 May 2000, substorm events of 10 June 2001 and 25 June 2000, and also during a prolonged quiet period (2 May 2001) when the plasmasphere was very extended. The formation of structures, like plumes and shoulders observed during periods of high geomagnetic activity, is quite well reproduced by the simulations. These structures are directly related to specific time sequences of Kp variations. The radial distances of the plasmapause are also reproduced, on average, by the model. Keywords. Magnetospheric physics (Plasmasphere; Storms and substorms; Solar wind magnetosphere interactions)

Analysis of differential GPS performance for marine users during solar maximum

GPS signals are refracted by the dispersive ionosphere, resulting in ranging errors dependent on both the given signal frequency and ionospheric total electron content. Such range errors translate into a degradation of positioning accuracies. While it is possible to mitigate the impact of ionospheric effects on GPS positioning applications through ionosphere modeling and/or differential techniques (DGPS), residual errors may persist in regions where steep gradients or localized irregularities in electron density exist, particularly during periods of high geomagnetic activity. Such effects are an issue for the reliable implementation of safety‐critical GPS systems. A solar maximum was observed in mid 2000 with associated degradations in GPS positioning accuracies. In this paper the impact of solar maximum on DGPS horizontal positioning applications is investigated. Analyses focus on determining limitations in horizontal positioning accuracies for operational marine DGPS systems. Long‐term analyses are conducted using data from permanent GPS reference networks in Canada, Brazil, and the United States. Several million observations are processed in this study during the years 1998–2000. Studies focus on large ionospheric gradients near the equatorial anomaly and at subauroral latitudes (associated with the main trough and storm‐enhanced densities). Results indicate that DGPS horizontal positioning accuracies are degraded by a factor of 2–5 relative to average values.

Observation of low frequency electromagnetic activity at 1000 km altitude

Abstract. We present a statistical study of low frequency fluctuations of electric and magnetic fields, commonly interpreted as Alfvénic activity. The data base consists of six months of electric and magnetic field measurements by the Astrid-2 microsatellite. The occurrence of the events is studied with respect to the location and general activity. Large regions of broadband Alfvénic activity are persistently observed in the cusp/cleft and, during the periods of high geo-magnetic activity, also in the pre-midnight sector of the auroral oval.Key words. Ionosphere (auroral ionosphere) – Space plasma physics (waves and instabilities) – Magnetospheric physics (magnetosphere-ionosphere interactions)

The northern auroral region as observed in nitric oxide

The distribution of thermospheric nitric oxide in the northern polar region has been measured from the Student Nitric Oxide Explorer (SNOE). A polar image of a one‐year average at 106 km shows the maximum density lies between 60° and 70° N geomagnetic latitude. The density around this auroral oval varies as a function of longitude with the larger densities occurring at western geomagnetic longitudes. A polar image of a second year of observations demonstrates the same latitudinal‐longitudinal density distribution indicating that the asymmetry is a persistent property of the auroral region. For a period of high geomagnetic activity, the nitric oxide observations indicate that the flux of precipitating electrons at 90° W geomagnetic longitude was 75% larger than the flux at 90° E geomagnetic longitude. We suggest that this asymmetry is caused by the longitudinal variation in the magnetic field strength around the auroral oval.

Application of ionospheric tomography to real‐time GPS carrier‐phase ambiguities Resolution, at scales of 400–1000 km and with high geomagnetic activity

The influence of the ionosphere can be one of the main obstacles to GPS carrier phase ambiguity resolution in real‐time, particularly over long baselines. This is important to all users of GPS requiring sub‐decimeter positioning, perhaps in real time, especially with high geomagnetic activity or close to the Solar Maximum. Therefore, it is desirable to have a precise estimation of the ionospheric delay in real‐time, to correct the data. In this paper we asses a real‐time tomographic model of the ionosphere created using dual‐frequency phase data simultaneously collected with the receivers of a network of stations in the USA and Canada, with separations of 400–1000 km, during a period of high geomagnetic activity (Kp=6). When the tomographic ionospheric correction is included, the resolution on‐the‐fly (OTF) of the widelane double‐differenced ambiguities at the reference stations is nearly 100% successful for satellite elevations above 20 degrees, while the resolution of the L1, L2 ambiguities at the rover is typically more than 80% successful.

WINDII measurements of nightglow enhancements in the South Atlantic Magnetic Anomaly Zone

Enhancements of the O(¹D) 630 nm and O(¹S) 558 nm volume emission rates were detected by WINDII, the Wind Imaging Interferometer on board the Upper Atmosphere Research Satellite, UARS, as its limb‐locked fields of view crossed the South Atlantic magnetic anomaly zone during periods of high geomagnetic activity. The enhancement attributed to electron precipitation is 20 R for the 630 nm red line and 3 R for the 558 nm green line, less than the natural variability of these nightglow emissions as seen from below. Nevertheless, statistical tests indicate with 95% confidence that the enhancements are significantly distinguishable from the natural variability. The red enhancement lies west of the green because eastward drifting trapped electrons move toward lower mirror altitudes in this region. These enhancements are energetically consistent with earlier measurements of electron fluxes in this region; we estimate the total precipitation energy deposition rate at a few megawatts.

Modeling thermospheric neutral density waves and holes in response to high latitude forcing

Numerical simulations have been performed to model the neutral density response to two substorms in March 1979. Observations of density from the Satellite Electrostatic Triaxial Accelerometer (SETA) during this interval revealed neutral density waves propagating from high latitudes in response to the substorms. For the first substorm, waves were seen on both the day and nightside in the Northern Hemisphere, and for the second, only strong nightside waves were detected. The data also revealed the formation of deep neutral density “holes” at high latitudes. To simulate the response, a coupled thermosphere ionosphere model was driven by an empirical substorm model designed to follow the various phases of the substorms. By tuning the magnitude of the energy injection and, in one case, rotating the spatial distribution of the sources, both the wave features on the day and nightside, and the neutral density holes were reproduced. The neutral density waves were found to be consistent with the passage of atmospheric gravity waves with propagation speeds of 600 to 700 m/s. The neutral density holes are dynamically driven, created by the high velocity neutral winds from ion-drag. During strong geomagnetic activity momentum forcing resulting from ion-drag drives neutral winds of several hundreds of m/s. Inertial forces on the gas parcels cause a divergence in the vortex-like circulation. Backpressure induced by the divergent wind field does not completely balance the flow, and air rises within the vortex core, to maintain continuity, and cools adiabatically to produce a low temperature. Due to the cooling that takes place, in spite of the strong Joule heating that must accompany the ion-drag, the cold vortex core appears as a density hole. The physical model is able to reproduce the magnitude and location of the density holes. The study indicates that physical models, with well-defined magnetospheric inputs, will be able to improve neutral density specification for orbital tracking during period of high geomagnetic activity.