High Geomagnetic Activity Research Articles

Circulation changes in the winter lower atmosphere and long-lasting solar/geomagnetic activity

Abstract. The paper describes the association between high long-lasting solar/geomagnetic activity and geopotential height (GPH) changes in the winter lower atmosphere, based on their development in the Northern Hemisphere in the winter periods (December–March) of 1950–1969 and 1970–2002. Solar/geomagnetic activity is characterised by the 60-day mean of the sunspot number R/by the 60-day mean of the daily sum of the Kp index. The GPH distributions in the lower atmosphere are described by 60-day anomalies from their long-term daily average at 20 hPa/850 hPa. The data have been adopted from the NCEP/NCAR reanalysis. The 60-day mean values of solar/geomagnetic activity and GPH anomalies were calculated in five-day steps over the whole winter period. The analysis was carried out using composite maps which represent their distribution of the GPH anomalies during high solar activity (R ≥ 100) and high geomagnetic activity (ΣKp ≥ 20). Analysis has shown that the distribution of GPH anomalies depends on solar activity, geomagnetic activity and the phase of winter period (early or late winter). The nature of this relationship then depends on the time interval involved, i.e. 1950–1969 or 1970–2002. Positive anomalies in the polar stratosphere (20 hPa) were detected during the whole winter periods of the years 1950–1969. Significant anomalies were detected in the lower troposphere (850 hPa) during the second half of the winter period. The distribution of GPH anomalies on the maps compiled with regard to solar activity was similar to the distribution on maps compiled with regard to geomagnetic activity. In the interval 1970–2002, significant negative GPH anomalies were detected in the stratosphere at high latitudes, and positive anomalies were detected in the region of low latitudes. The distribution of GPH anomalies in the lower troposphere was substantially affected by situations in which, together with high solar activity, also high geomagnetic activity occurred.

Estimating the capture and loss of cold plasma from ionospheric outflow

An important source of magnetospheric plasma is cold plasma from the terrestrial ionosphere. Low energy ions travel along the magnetic field lines and enter the magnetospheric lobes where they are convected toward the tail plasma sheet. Recent observations indicate that the field aligned ion outflow velocity is sometimes much higher than the convection toward the central plasma sheet. A substantial amount of plasma therefore escapes downtail without ever reaching the central plasma sheet. In this work, we use Cluster measurements of cold plasma outflow and lobe convection velocities combined with models of the magnetic field in an attempt to determine the fate of the outflowing ions and to quantify the amount of plasma lost downtail. The results show that both the circulation of plasma and the direct tailward escape of ions varies significantly with magnetospheric conditions. For strong solar wind driving with a southward interplanetary magnetic field, also typically associated with high geomagnetic activity, most of the outflowing plasma is convected to the plasma sheet and recirculated. For periods with northward interplanetary magnetic field, the convection is nearly stagnant, whereas the outflow, although limited, still persists. The dominant part of the outflowing ions escape downtail and are directly lost into the solar wind under such conditions.

Anomalous TEC variations associated with the powerful Tohoku earthquake of 11 March 2011

Abstract. On 11 March 2011 at 14:46:23 LT, the 4th largest earthquake ever recorded with a magnitude of 9.0 occurred near the northeast coast of Honshu in Japan (38.322° N, 142.369° E, Focal depth 29.0 km). In order to acknowledge the capabilities of Total Electron Content (TEC) ionospheric precursor, in this study four methods including mean, median, wavelet transform, and Kalman filter have been applied to detect anomalous TEC variations concerning the Tohoku earthquake. The duration of the TEC time series dataset is 49 days at a time resolution of 2 h. All four methods detected a considerable number of anomalous occurrences during 1 to 10 days prior to the earthquake in a period of high geomagnetic activities. In this study, geomagnetic indices (i.e. Dst, Kp, Ap and F10.7) were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic and solar activities. A good agreement in results was found between the different applied anomaly detection methods on TEC data.

Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite

In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65° and +65° in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

Comparative Analysis of the Response of Microcirculation Parameters and Blood Pressure to Geomagnetic Activity in Healthy People

We analyze the results of daily laser Doppler flowmetry monitoring of blood microcirculation parameters in 9 healthy volunteers performed in 2006-2009. Dependence of microcirculation and BP parameters on geomagnetic activity was analyzed separately in each volunteer (the influence of ambient temperature was previously excluded). Significantly increased parameters of microcirculation in response to higher geomagnetic activity were found in 4 volunteers (44%) and elevated BP in 1 volunteer; in other cases, no reaction was detected. It was shown that individual sensitivity to geomagnetic activity is proportional to its mean level during the period of measurement. Since blood perfusion volume in tissues directly depends on peripheral vascular resistance, we can conclude that under conditions of high geomagnetic activity microvascular tone varies to a greater extent than the tone of major vessels.

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.

A Three-Dimensional Ray Tracing Study on Whistler-Mode Chorus During Geomagnetic Activities

A three-dimensional ray tracing study of a whistler-mode chorus is conducted for different geomagnetic activities by using a global core plasma density model. For the upper-band chorus, the initial azimuthal wave angle affects slightly the projection of ray trajectories onto the plane , but controls the longitudinal propagation. The trajectory of the upper-band chorus is strongly associated with the plasmapause and the magnetic local time (MLT) of chorus source region. For the high geomagnetic activity, the chorus trajectory moves inward together with the plasmapause. In the bulge region, the plasmapause extends outward, while the chorus trajectory moves outward together with the plasmapause. For moderately or high geomagnetic activity, the lower-band chorus suffers low hybrid resonance (LHR) reflection before it reaches the plasmapause, leading to a weak correlation with the geomagnetic activity and magnetic local time of the chorus source region. For low geomagnetic activity, the lower-band chorus may be reflected firstly at the plasmapause instead of suffering LHR reflection, exhibiting a propagation characteristic similar to that of the upper-band chorus. The results provide a new insight into the propagation characteristics of the chorus for different geomagnetic activities and contribute to further understanding of the acceleration of energetic electron by a chorus wave.

On the statistical relation between ion upflow and naturally enhanced ion-acoustic lines observed with the EISCAT Svalbard radar

[1] We have investigated characteristics of ion upflow and naturally enhanced ion-acoustic lines (NEIALs) based on the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) data continuously obtained between March 2007 and February 2008. For the ion upflow study we have used approximately 78,000 field-aligned profiles obtained with the ESR. For the NEIAL study we have identified approximately 1500 NEIALs in the ESR data at altitudes between 100 and 500 km. The occurrence frequency of ion upflow shows two peaks, at about 0800 and 1300 magnetic local time (MLT), while only one strong peak is seen around 0900 MLT for NEIALs. The upward ion flux also has only one peak around 1100–1300 MLT. The occurrence frequency of ion upflow varies strongly over season. It is higher in winter than in summer, whereas NEIALs are more frequent in summer than in winter. NEIALs frequently occur under high geomagnetic activity and also high solar activity conditions. Approximately 10% of NEIALs in the F region ionosphere were accompanied by NEIALs in the E region (occurred at altitudes below 200 km). About half of the E region enhanced echoes did not have an F region counterpart. Upshifted NEIALs dominate in the E region whereas downshifted NEIALs are usually stronger above an altitude of 300 km. The high occurrence frequency of NEIALs in the prenoon region (0800–1000 MLT) might be associated with acceleration of thermal ions to suprathermal ones. At the same MLT and geomagnetic latitude suprathermal ions and broadband extremely low frequency (BBELF) wave activity have been observed, according to previous studies.

A statistical investigation of the Cowling channel efficiency in the auroral zone

[1] The Cowling channel mechanism describes the creation of a secondary polarization electric field at sharp conductance boundaries in the ionosphere due to excess charges for the case in which the release of these charges to the magnetosphere is fully or partially impeded. The secondary currents generated by the polarization electric field effectively modify the effective ionospheric conductivity inside the Cowling channel. While the Cowling mechanism is generally accepted for the equatorial electrojet, there is a long-standing discussion about the importance of this mechanism and its efficiency in the auroral electrojet. We present a statistical investigation that enables us to identify the most probable geospace conditions and MLT locations for a high Cowling efficiency. This investigation is based on more than 1600 meridional profiles of data from the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment (MIRACLE) network in Scandinavia, in particular, ground magnetic field data from the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network and electric field data from the Scandinavian Twin Auroral Radar Experiment (STARE) radar, supported with pointwise ionospheric conductance measurements from the European Incoherent Scatter (EISCAT) radar. We analyze the data in the framework of a 3-D ionospheric model, but our data set is filtered so that only electrojet-type situations are included so that the gradients of all measured quantities in longitudinal direction can be neglected. The analysis results in a steep peak of high Cowling channel efficiency probability in the early morning sector (0245–0645 MLT), with the largest probability around 0500 MLT and for medium and high geomagnetic activity. In agreement with an earlier single-event study by Amm and Fujii (2008), this indicates that the Cowling mechanism may be most effective in the early morning part of the central substorm bulge. Further, our analysis results in an almost monotonic increase of the probability of high Cowling channel efficiency with increasing geomagnetic activity.

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.

Geomagnetic activity effects on plasma sheet energy conversion

Abstract. In this article we use three years (2001, 2002, and 2004) of Cluster plasma sheet data to investigate what happens to localized energy conversion regions (ECRs) in the plasma sheet during times of high magnetospheric activity. By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have studied the influence on Concentrated Load Regions (CLRs) and Concentrated Generator Regions (CGRs) from variations in the geomagnetic disturbance level as expressed by the Kp, the AE, and the Dst indices. We find that the ECR occurrence frequency increases during higher magnetospheric activities, and that the ECRs become stronger. This is true both for CLRs and for CGRs, and the localized energy conversion therefore concerns energy conversion in both directions between the particles and the fields in the plasma sheet. A higher geomagnetic activity hence increases the general level of energy conversion in the plasma sheet. Moreover, we have shown that CLRs live longer during magnetically disturbed times, hence converting more electromagnetic energy. The CGR lifetime, on the other hand, seems to be unaffected by the geomagnetic activity level. The evidence for increased energy conversion during geomagnetically disturbed times is most clear for Kp and for AE, but there are also some indications that energy conversion increases during large negative Dst. This is consistent with the plasma sheet magnetically mapping to the auroral zone, and therefore being more tightly coupled to auroral activities and variations in the AE and Kp indices, than to variations in the ring current region as described by the Dst index.

Propagation Characteristics of Whistler-Mode Chorus during Geomagnetic Activities

A recently introduced ray-tracing method is adopted to study the propagation characteristics of whistler-mode chorus during different geomagnetic activities by using a global core plasma density model. Numerical calculations show that chorus waves tend to settle on a preferable magnetic shell L in the vicinity of the plasmapause. During high geomagnetic activity, the plasmapause position moves inward close to the Earth and chorus trajectories move inward together with plasmapause. The trajectory move closer to the plasmapause as 9 increases. Chorus wave with lower frequencies will reflect multiple times while chorus wave with higher frequencies reflect once at the plasmapause before settling on the vicinity of the plasmapause. The current results present a first detailed study on the propagation characteristics of chorus during geomagnetic activities, and may account for the observation that chorus tends to be present in the vicinity of the plasmapause.

High-latitude geomagnetically induced current events observed on very low frequency radio wave receiver systems

[1] Noise burst events observed at Sodankyla, Finland, in the frequency range 20–25 kHz during January–April 2005 last up to 4 s, occur more often at midnight, are associated with high geomagnetic activity, and exhibit a quasi-constant amplitude perturbation ∼15 dB above the background noise levels. We considered the possibility that the events could be caused by lightning noise breakthrough. The association of the noise burst events with local midnight and high geomagnetic activity argues against a lightning link, as well as the lack of close thunderstorm location relative to Sodankyla during noise periods. While energetic electron precipitation is also associated with high geomagnetic activity, we showed that they occur at different times and exhibit significantly different amplitude characteristics. Finally, we compared in detail the geomagnetic induced current (GIC) in the Scottish power system in southern Scotland, during a storm event that occurred on 15 May 2005, with the noise burst event rate at Sodankyla. We found that the onset time and variability of the Scottish GIC activity was well matched by the variability in the noise burst event rate, particularly the high-frequency component of the GIC fluctuations. The technique used in our study of observing at a narrow band of frequencies allows GIC measurements to be made in built-up areas where mains interference is a problem for other experiments, such as magnetometers.

Revised comparison and analysis of severe magnetic storm effects measured over Istanbul and Rome

Geomagnetic Storms (GS) and Ionospheric Storms (IS) for high geomagnetic activity conditions are studied in Istanbul (IST) and in Rome (RO). Further and revised results that led to new interpretations are briefly presented here following a previous paper on the severe storm effects on the ionosphere over Istanbul. The series of storms started on 28th October 1968 and went on to 2nd November 1968 with the geomagnetic index Kp reaching values up to 8. Deviations of the critical frequency of the F 2 layer, Δ foF 2(%), from monthly medians up to 100% were observed. Power spectral results show here that not only the Diurnal Planetary Waves (PW) of 2.3 day periodicity but also tidal waves with semidiurnal (12h), teridiurnal (8h) and quaterdiurnal (6h) characteristic times are present.

Ground-based observations of auroras under the sunlit conditions

The results of the ground-based optical observations of sunlit auroras, performed at Lovozero and Apatity observatories on April 10 (event 1) and April 27, 2007(event 2), are presented. The observations were performed in the (OI) 557.7 nm emission, using a new equipment based on a Fabry-Perot interferometer connected to a PhotonMAX CCD camera. During event 1, the observations were performed in the Harang discontinuity region at a low magnetic disturbance. It has been indicated that an auroral arc was located in the polar part of the eastward electrojet, and the arc position coincides with the equatorward boundary of structured precipitation (b2e). During event 2, auroras were observed within the average statistical boundaries of the auroral oval and the region of structured precipitation under the conditions of rather high geomagnetic activity. However, during the period of low geomagnetic activity, discrete auroras were registered at a geomagnetic latitude of ~64° on that day, which is 3°—4° equatorward of the structured precipitation region. Such a low latitudinal position of auroras can be explained by the effect of a high solar wind velocity, which was ~580 km/s during the period of observations.

Acute Myocardial Infarction (AMI) and Intermediate Coronary Syndrome (ICS)

In recent studies it was shown that blood co-agulation and inflammation markers are raising at high geomagnetic activity; acute myocardial infarction and all his subtypes, mostly related to atheromatous plaque disruption with higher Cosmic Ray (Neutron) activity. The aim of this study was to explore AMI and ICS differences by concomitant physical conditions, accompany-ing each of these acute coronary syndromes. The data was a part of MONICA international study in Kaunas, Lithuania in years 2000-2005 (72 consecutive months). 4633 patients with AMI (2461 men) and 961 with ICS (654 men), (age up to 65) were studied. For comparison four indices of Solar (SA), three of Geomagnetic (GMA), Cosmic Ray (CRA) measured by Neutron activity imp/min. were used. Cosmophysical data were from space science institutions in the USA and Russia. Pearson correlation coefficients and their probabilities were obtained.Monthly num-ber of AMI and ICS shows different links with the physical parameters: AMI were significantly in-verse related to SA (r=-0.4, p=0.0021) and direct to CRA (Neutron) activity (r=0.23, p=0.048). ICS was not correlated with these two parameters, but show significant links to GMA (r=0.25, p=0.037). Gender differences were evident, men more close related to changes in the mentioned physical parameters.Conclusion: 1. Monthly nu- mber of AMI and ICS is different related to fluc-tuations of environmental physical parameters. 2. The described connections can affect differ-ences in the pathogenesis of these forms of Acute Coronary Insufficiency.

Effects of geomagnetic disturbances in power spectra of atmospheric waves in the dynamo region of the ionosphere

The dynamics of wave disturbances in the ionospheric E region in the band of periods of thermal tidal waves and waves of planetary scales (T = 48, 72, and 192 h) has been studied based on the variations in the horizontal component of the geomagnetic field, observed at Paratunka and Barrow observatories in September–October 1999. It has been found that, at midlatitudes during high geomagnetic activity, the intensity of oscillations in the power spectra with T = 24 and 12 h varies with a periodicity of 16 days different from the periodicity of changes in the ΣKp index. The maximal deviations of these periods from the values under quiet conditions coincide with the maximal changes in the ΣKp index. The variations in the 48–192 h band of periods (especially with T ∼192 h) intensify simultaneously with increasing geomagnetic activity. The intensity of this harmonic is several times as high as that of the harmonic with T ∼ 24 h. The periodicity of changes in the harmonics intensity within the 48–192 h band coincides with the periodicity of changes in the ΣKp index. In the polar ionosphere, the effect of high geomagnetic activity is observed as an increase in the variations with a quasi-period of T ∼ 24 h and as an appearance of variations in the 48–192 h band with the periodicity coinciding with the maximums in the ΣKp index variations.

An association between geomagnetic activity and dream bizarreness

Daily disturbances of the earth's magnetic field produce variations in geomagnetic activity (GMA) that are reportedly associated with widespread effects on human health and behaviour. Some of these effects could be mediated by an established influence of GMA on the secretion of melatonin. There is evidence from unrelated research that melatonin influences dream bizarreness, and it is hypothesised here that there is an association between GMA and dream bizarreness. Also reported is a preliminary test of this hypothesis, a case study in which the dreams recorded over 6.5 years by a young adult male were analysed. Reports of dreams from the second of two consecutive days of either low or high GMA (K index sum < or =6 or > or = 28) were self-rated for bizarreness on a 1-5 scale. Dreams from low GMA periods (n=69, median bizarreness=4) were found to be significantly more bizarre than dreams from high GMA periods (n=85, median bizarreness=3; p=0.006), supporting the hypothesised association between GMA and dream bizarreness. Studies with larger samples are needed to verify this association, and to determine the extent to which melatonin may be involved. Establishing that there is an association between GMA and dream bizarreness would have relevance for neurophysiological theories of dreaming, and for models of psychotic symptoms resembling bizarre dream events.

Day-time variations of foF2 connected to strong earthquakes

Abstract. The statistical analysis of the characteristic frequency foF2 of the Earth's ionosphere averaged over mid-day hours – from 11:00 till 17:00 h LT – is carried out. Disturbances of foF2 connected to earthquakes are considered on the background of seasonal, geomagnetic, 11-years and 27-days solar variations. A special normalized parameter F is introduced, which represents the almost seasonal-independent part of foF2. Days with high solar (Wolf number &gt;100) and geomagnetic (∑Kp&gt;30) activity are excluded from the analysis. Events with magnitude M&gt;5, distance from the sounding station R&lt;500 km and depth h&lt;70 km are taken into account. The superimposed epoches' method is used to determine the temporal dependence of F. It is found that F increases about 3–6 days before the earthquakes and then decreases one day – two days before the shock. The decreased values of F continue to exist two-three days after events with M&gt;5.5. The obtained phenomenon depends on the magnitude of the earthquake. For events with M&gt;5.5, the reliability of the effect is larger than 95%. For data of more than 80 earthquakes in the vicinity of Petropavlovsk-Kamchatsky and more than 200 earthquakes in the vicinity of Tokyo analogous results are obtained.

Ionospheric ions in the near-Earth magnetotail

[1] We report studies of the relationship between geomagnetic storms and the spatial distribution of cold ions, mostly of ionospheric origin, in the near-Earth magnetotail using in situ particle and field measurements from the Polar spacecraft, solar wind measurements from the ACE spacecraft, and ground geomagnetic indices, during the years from 2000 to 2005. We find local time and latitude-dependent distributions of the plasma moments of cold ions at various levels of geomagnetic storms characterized by the Sym-H and Dst indices. (1) Denser cold ions were observed at the duskside (N > 10 cm−3 compared with 1 cm−3 on average): consistent with the formation of plasma plumes and enhanced bulge region formed as the cold ions wrapped under corotation. (2) Higher temperatures were observed in the auroral oval regions, and a larger temperature anisotropy was observed at the dawnside. (3) Heating processes were strongest near midnight and in the auroral oval regions, which map to PSBL or CPS, except during extremely high geomagnetic activity levels, when heating occurred at high latitudes toward the dawnside, which map to the plasma mantle or distant magnetotail. We interpret these variations as results of ionospheric outflows and plasmaspheric expansion interacting with enhancements of near-Earth magnetospheric convection and geomagnetic-storm-related heating processes in the magnetotail.