Interplanetary Field Research Articles

Distinctive effects of interplanetary electric field and substorm on nighttime equatorial F layer: A case study

A geomagnetic storm event is identified wherein the base of the equatorial F layer (h′F) over dip equator moved unusually upward till premidnight hours and descended thereafter. The h′F variation is linearly correlated with the variation in the smoothed auroral electrojet index (AE) which varies slowly. The fast fluctuations (residuals) with periodicity ∼42 min in the vertical plasma drift are found to be causally related with the fast fluctuations in the dawn‐to‐dusk component of interplanetary electric field (IEFy) and interestingly, not with the fast fluctuations in AE. However, during the interval when a substorm was triggered in association with sharp transitions in IEFy polarity, the drift fluctuations follow the AE fluctuations and are out of phase with IEFy fluctuations. The investigation demonstrates distinctive effects of IEFy and substorm‐related current systems on the zonal electric field over dip equator in the premidnight hours during geomagnetic storms.

Abnormal vertical drifts of equatorial plasma before dawn and after sunset during the storm of 29–30 October 2003

The ROCSAT‐1 observations of vertical ion velocity in low latitudes during the main phase of the storm of 29–30 October 2003 show an occurrence of abnormally large downward plasma drift before dawn and pronounced upward drift after sunset. At the time of the occurrence of the abnormal vertical plasma drifts at the terminators the background ionosphere shows an upward drift during 0800‐2000 LT and downward drift during 2000‐0800 LT. The global‐scale change in the vertical plasma drifts and its coincidence with the onset of dawn‐to‐dusk interplanetary electric field indicate that the disturbance drifts are associated with the penetration electric field (PE). The nightward PE at the terminators induces an accumulation of positive charges at the terminators; polarization electric fields develop by the charge accumulation; and the addition of the PE and polarization electric field can produce pronounced downward drift before dawn and upward drift after sunset.

Effect of magnetic storms in variations in the atmospheric electric field at midlatitudes

The observations of the variations in the vertical component of the atmospheric electric field (E z ) at Swider midlatitude Poland observatory (geomagnetic latitude 47.8°) under the conditions of fair weather during 14 magnetic storms have been analyzed. The effect of the magnetic storm main phase in the daytime midlatitude variations in E z in the absence of local geomagnetic disturbances has been detected for the first time. Considerable (∼100–300 V m−1) decreases in the electric field strength (E z ) at Swider observatory were observed in daytime simultaneously with the substorm onset in the nighttime sector of auroral latitudes (College observatory). The detected effects indicate that an intensification of the interplanetary electric field during the magnetic storm main phase, the development of magnetospheric substorms, and precipitation of energetic electrons into the nighttime auroral ionosphere can result in considerable disturbances in the midlatitude atmospheric electric field.

Local and nonlocal geometry of interplanetary coronal mass ejections: Galactic cosmic ray (GCR) short‐period variations and magnetic field modeling

Energetic galactic cosmic ray (GCR) particles, arriving within the solar system, are modulated by the overall interplanetary field carried in the solar wind. Localized disturbances related to solar activity cause further reduction in intensity, the largest being Forbush decreases in which fluxes can fall ∼20% over a few days. Understanding Forbush decreases leads to a better understanding of the magnetic field structure related to shock waves and fast streams originating at the Sun since the propagation characteristics of the GCR probe much larger regions of space than do individual spacecraft instruments. We examined the temporal history of the integral GCR fluence (≥100 MeV) measured by the high‐sensitivity telescope (HIST) aboard the Polar spacecraft, along with the solar wind magnetic field and plasma data from the ACE spacecraft during a 40‐day period encompassing the 25 September 1998 Forbush decrease. We also examined the Forbush and (energetic storm particles) ESP event on 28 October 2003. It is the use of HIST in a high‐counting‐rate integral mode that allows previously poorly seen, short‐scale depressions in the GCR fluxes to be observed, adding crucial information on the origin of GCR modulation. Variability on time scales within the frequency range 0.001–1.0 mHz is detected. This paper concentrates on investigating four simple models for explaining short‐term reductions in the GCR intensity of both small and large amplitude. Specifically, these models are a local increase in magnetic scattering power, the passage of a shock discontinuity, and the passage of a tangential discontinuity or magnetic rope in the solar wind plasma. Analysis of the short‐scale GCR depressions during a test period in September through October 1998 shows that they are not correlated with changes in magnetic scattering power or fluctuations in solar wind speed or plasma density. However, magnetic field and plasma data during the test period of Forbush decrease strongly suggest the presence of an interplanetary coronal mass ejection (ICME). Use of a non‐force‐free magnetic rope model in conjunction with the energetic particle data allows modeling of the geometry of the ICME in terms of a magnetic cloud topology. It is only this cloud configuration that allows a satisfactory explanation of the magnitude of the Forbush event of 25 September 1998. Calculations made during the test period point to short‐scale GCR depressions being caused by either small‐scale magnetic flux rope structures or possibly tangential discontinuities in the solar wind.

Derivation of inner magnetospheric electric field (UNH-IMEF) model using Cluster data set

Abstract. We derive an inner magnetospheric electric field (UNH-IMEF) model at L=2–10 using primarily Cluster electric field data for more than 5 years between February 2001 and October 2006. This electric field data set is divided into several ranges of the interplanetary electric field (IEF) values measured by ACE. As ring current simulations which require electric field as an input parameter are often performed at L=2–6.6, we have included statistical results from ground radars and low altitude satellites inside the perigee of Cluster in our data set (L~4). Electric potential patterns are derived from the average electric fields by solving an inverse problem. The electric potential pattern for small IEF values is probably affected by the ionospheric dynamo. The magnitudes of the electric field increase around the evening local time as IEF increases, presumably due to the sub-auroral polarization stream (SAPS). Another region with enhanced electric fields during large IEF periods is located around 9 MLT at L>8, which is possibly related to solar wind-magnetosphere coupling. Our potential patterns are consistent with those derived from self-consistent simulations. As the potential patterns can be interpolated/extrapolated to any discrete IEF value within measured ranges, we thus derive an empirical electric potential model. The performance of the model is evaluated by comparing the electric field derived from the model with original one measured by Cluster and mapped to the equator. The model is open to the public through our website.

Coronal Holes and Open Magnetic Flux

Coronal holes are low-density regions of the corona which appear dark in X-rays and which contain “open” magnetic flux, along which plasma escapes into the heliosphere. Like the rest of the Sun’s large-scale field, the open flux originates in active regions but is subsequently redistributed over the solar surface by transport processes, eventually forming the polar coronal holes. The total open flux and radial interplanetary field component vary roughly as the Sun’s total dipole strength, which tends to peak a few years after sunspot maximum. An inverse correlation exists between the rate of flux-tube expansion in coronal holes and the solar wind speed at 1 AU. In the rapidly diverging fields present at the polar hole boundaries and near active regions, the bulk of the heating occurs at low heights, leading to an increase in the mass flux density at the Sun and a decrease in the asymptotic wind speed. The quasi-rigid rotation of coronal holes is maintained by continual footpoint exchanges between open and closed field lines, with the reconnection taking place at the streamer cusps. At much lower heights within the hole interiors, “interchange reconnection” between small bipoles and the overlying open flux also gives rise to coronal jets and polar plumes.

Dependence of SuperDARN cross polar cap potential upon the solar wind electric field and magnetopause subsolar distance

Dependence of the cross polar cap potential (CPCP) upon the interplanetary electric field (IEF), solar wind ram pressure, and magnetopause standoff distance (RMS) are investigated by considering the Super Dual Auroral Radar Network (SuperDARN) HF radar data on the CPCP and information on the solar wind and interplanetary magnetic field from ACE satellite. Data of up to IEF ∼12 mV/m are available. The CPCP scatterplot versus IEF shows a linear increase between 0 and ∼3 mV/m. For larger IEFs, the rate of the CPCP growth decreases, and the dependence eventually saturates. If the same data are arranged in groups of RMS values, linear dependences were found for each group, but the slope of the regression line increases with RMS. The inferred linear fit lines of CPCP versus IEF for various RMS groups intersect each other at IEF ∼3 mV/m. This number is found to be unique because for the IEF above it (below it), the CPCP decreases (increases) with the solar wind ram pressure. This value also corresponds to the condition of the solar wind magnetic field at the subsolar point to be equal to the Earth's dipole magnetic field, as previously reported by Siscoe et al. (2002). Presented analysis suggests that the magnetopause standoff distance (the length of the merging X line) is an important factor in the CPCP saturation.

Solar concept of flux transport by interchange reconnection applied to the magnetosphere

The traditional concept of steady state convection of magnetic field‐line foot points in Earth's ionosphere driven by reconnection between the interplanetary and geomagnetic fields implies that those foot points follow closed contours of circulation. Remote reconnection that occurs when the foot points cross the polar cap boundary controls whether the field lines are open or closed, but the foot points remain firmly rooted to their paths around the closed circulation cells. In steady state MHD models, however, this concept of convection breaks down owing to interchange reconnection between open and closed field lines. In the solar heliospheric community, interchange reconnection has long been understood as a means of flux transport. In the magnetosphere, flux transport by interchange reconnection causes field‐line foot points to jump, or saltate, from one side of the polar cap to the other as part of the steady state circulation. We develop a definitive method for identifying interchange reconnection in an MHD model and illustrate the resultant foot point saltation.

Atmospheric circuit influences on ground‐level pressure in the Antarctic and Arctic

Pressure variations at 11 Antarctic sites and 7 Arctic sites have been examined and show significant correlations with a daily proxy for the output of the meteorological generators of the global atmospheric circuit. This proxy is derived from vertical electric field measurements made at Vostok on the Antarctic ice plateau. Taken with the finding of proportionate pressure variations correlated with atmospheric circuit changes owing to coupling with the interplanetary electric field, particularly for the Antarctic plateau (magnetic latitude > 83°) region, this provides experimental evidence that a small portion of the surface pressure variations are due to the influence of the global atmospheric circuit. The response to the interplanetary electric field is an example of Sun‐weather coupling. To evaluate it, the daily average interplanetary magnetic field (IMF) east‐west component (By) is used as a proxy for the north–south interplanetary electric field, which produces opposite ionospheric potential changes in the northern and southern polar caps. The correlation with IMF By for the pressure variations for the Antarctic sites for a solar cycle (1995–2005) is small (0.9% average covariance for the magnetic latitude > 83° sites) but significant (99.7% confidence level). The Arctic stations show a negative regression between pressure variations and IMF By, a relationship expected if the linkage process operates by the atmospheric circuit, but it is only found when the interval is restricted to the peak of the sunspot cycle (1999–2002).

Reverse convection potential saturation during northward IMF

We report the results of an investigation of the reverse convection potentials in the day side high latitude ionosphere during periods of steady northward interplanetary magnetic field (IMF). While it has been shown that the polar cap potential in the ionosphere exhibits non‐linear saturation behavior when the IMF becomes increasingly southward, it has yet to be shown whether the high latitude reverse convection cells in response to increasingly northward IMF exhibit similar behavior. We use solar wind data from the ACE satellite from 1998 to 2005 to search for events in the solar wind when the IMF is northward and the interplanetary electric field is stable for more than 40 minutes. We then use bin‐averaged SuperDARN convection data and apply a spherical harmonic fit to calculate the average potential pattern for each northward IMF bin. Results show that the reverse convection cells do, in fact, exhibit non‐linear saturation behavior. The saturation potential is approximately 20 kV and is achieved when the electric coupling function reaches between 18 and 30 kV/RE.

Magnetospheric source of UHF radio bursts at mid-latitudes during the magnetic storm on October 22, 1999

We discuss the results of our simultaneous observations of interplanetary and geomagnetic field fluctuations as well as solar wind parameters and meter radio emission in near-Earth space at mid-latitudes (near Kharkov) based on ground measurements before and during a unique magnetic storm on October 22, 1999. The electron flux dynamics in interplanetary space, geostationary orbit, and the magnetosphere is analyzed to find the interconnection with UHF radio background bursts at a frequency of 151 MHz. We conclude that the acceleration processes in the inner magnetospheric layers affect the generation processes of high-frequency radio bursts and that this phenomenon should be studied further using the SINP (MSU) instruments onboard the CORONAS-F satellite.

Open magnetic flux tubes in the corona and the transport of solar energetic particles

We investigate how magnetic fields guide energetic particles through the corona into interplanetary space and eventually to a spacecraft near the Earth. A set of seven simple particle events is studied, where energetic electrons (30–500 keV; Wind spacecraft) or protons (5–55 MeV; SoHO) were released together with low-energy electron beams producing metric-to-kilometric type III emission. Imaging of the coronal (metre-wave) part of this emission with the Nancay Radioheliograph is used to identify the open flux tubes that guide these electrons – and by inference all particles detected at 1 AU. Open coronal field lines are also computed using potential magnetic field extrapolations, constrained by a source surface and by SoHO/MDI measurements in the photosphere (code by Schrijver and DeRosa). We find that in all events the type III radio sources lie in open flux tubes in the potential magnetic field extrapolations. The open flux tubes are rooted in small parts of the parent active region, covering a heliocentric angle of a few degrees in the photosphere. But they expand rapidly above the neighbouring closed magnetic structures and cover several tens of degrees in longitude on the source surface. Some of these open field lines are found to connect the parent active region to the footpoint of the nominal Parker spiral on the source surface, within the uncertainty of about ±10 ◦ inherent to the evaluation of its connection longitude. This is so even when the parent active region is as far as 50 ◦ away. In two cases where the coronal flux tubes point to high heliolatitudes, the detection of Langmuir waves at the Wind spacecraft in the ecliptic plane suggests that the interplanetary field lines curve down to the ecliptic before reaching 1 AU. We conclude that non-radial open flux tubes in the corona can transport particles over several tens of degrees in longitude even in simple impulsive particle events. In all events we studied, potential magnetic field models give an adequate description of these structures.

Storm-time ionization enhancements at the topside low-latitude ionosphere

Abstract. Ion density enhancements at the topside low-latitude ionosphere during a Bastille storm on 15–16 July 2000 and Halloween storms on 29–31 October 2003 were studied using data from ROCSAT-1/IPEI experiment. Prominent ion density enhancements demonstrate similar temporal dynamics both in the sunlit and in the nightside hemispheres. The ion density increases dramatically (up to two orders of magnitude) during the main phase of the geomagnetic storms and reaches peak values at the storm maximum. The density enhancements are mostly localized in the region of a South Atlantic Anomaly (SAA), which is characterized by very intense fluxes of energetic particles. The dynamics of near-Earth radiation was studied using SAMPEX/LEICA data on >0.6 MeV electrons and >0.8 MeV protons at around 600 km altitude. During the magnetic storms the energetic particle fluxes in the SAA region and in its vicinity increase more than three orders of magnitude. The location of increased fluxes overlaps well with the regions of ion density enhancements. Two mechanisms were considered to be responsible for the generation of storm-time ion density enhancements: prompt penetration of the interplanetary electric field and abundant ionization of the ionosphere by enhanced precipitation of energetic particles from the radiation belt.

Role of overshielding electric field on the development of pre-midnight plume event: Simulation results

An investigation involving nonlinear numerical simulation has been undertaken based on the observations of two events involving the reversal of nighttime zonal electric field to eastward direction over equatorial region due to the overshielding effect associated with interplanetary electric field. In one of the events, the ionospheric alterations brought forth by the prompt penetration event lead to the triggering of an equatorial spread F (ESF) event around 2040 IST and a plume structure during pre-midnight hours due to overshielding effect. In another observation, the ESF was found to be absent. The two-dimensional modeling investigation revealed that the storm-induced eastward electric field during nighttime over equatorial region is a necessary but not a sufficient condition for the development of the pre-midnight plume structure in the lower F-region altitude. The large scale size (240 km) perturbation amplitude of 5% is found to be insufficient for the development of late night plume event within 2000 s. A pre-seed in varying degrees in a localized altitude region depending upon the background ionospheric conditions, is found to be required for the development of the pre-midnight plume event. The confined ESF irregularities developed in the post-evening hours in a limited altitude range are suggested to provide such seed perturbation. The importance of the pre-seeded structure for the development of pre-midnight plume event is brought out from this investigation. The roles of the electron density scale length and the peak height of the F layer in deciding the required amplitudes of perturbation are also evaluated. This, in turn, can throw light on the night-to-night variability of storm-time ESF when a typical eastward perturbation electric field is operative during pre-midnight hours. The role of off-equatorial E region conductivity is also discussed.

An advanced approach to finding magnetometer zero levels in the interplanetary magnetic field

For a magnetometer that measures weak interplanetary fields, the in-flight determination of zero levels is a crucial step of the overall calibration procedure. This task is more difficult when a time-varying magnetic field of the spacecraft interferes with the surrounding natural magnetic field or when the spacecraft spends only short periods of time in the interplanetary magnetic field. Thus it is important to examine the algorithms by which these zero levels are determined, and optimize them. We find that the method presented by Davis and Smith (1968 EOS Trans. AGU 49 257) has significant mathematical advantages over that published by Belcher (1973 J. Geophys. Res. 71 5509) as well as over the correlation technique published by Hedgecock (1975 Space Sci. Instrum. 1 83–90). We present an alternative derivation of the Davis–Smith method which illustrates that it is also a correlation technique. It also works with first differences as well as filtered data as input. In contrast to the postulate by Hedgecock (1975 Space Sci. Instrum. 1 83–90), we find that using first differences in general provides no advantage in determining the zero levels. Our new algorithm obtains zero levels by searching for pure rotations of the interplanetary magnetic field, with a set of sophisticated selection criteria. With our algorithm, we require shorter periods (of the order of a few hours, depending on solar wind conditions) of interplanetary data for accurate zero level determination than previously published algorithms.

남쪽방향 행성간 자기장에 의해 발생한 자기 폭풍 동안 한반도 상공의 총 전자수 함유량 변화

행성간 자기장(Interplanetary Magnetic Field)이 남쪽방향으로 전환되면서 발생된 2003년 자기폭풍 동안 한반도 상공 전리층의 총 전자수 함유량(Total Electron Content, TEC) 변화에 대해 알아보았다. 남쪽방향의 행성간 자기장과 지구 자기장의 상호작용에 의해 고위도에서 유도된 전기장과 저위도 전리층으로 전파된 전기장이 저위도 지역의 TEC 증가와 관련 있는 것으로 생각된다. 데이터 분석결과 2003년 6월 16일에 발생한 이벤트 동안에는 낮 지역 TEC 값이 약 15% 증가하였다. F2층의 최대 높이를 나타내는 hmF2는 300km 까지 상승되었으며, 수직방향 <TEX>$E{\times}B$</TEX> 표류운동은 아랫방향으로 나타났다. 이것은 남쪽방향의 행성간 자기장 동안 고위도 지역으로 유입된 에너지에 의해 발생한 전리층의 교란된 다이나모 전기장이 TEC을 증가시킨 것으로 추정된다. 그러나 11월 20일에 발생한 이벤트 동안에는 전리층으로 전파된 서쪽방향 전기장에 의해 밤 지역 TEC 갈이 약 10% 증가한 것으로 보여 진다. 행성간 자기장이 남쪽방향으로 전환됨과 동시에 hmF2 높이는 200km까지 감소되었으며, 아랫방향 <TEX>$E{\times}B$</TEX> 표류운동이 나타났다. 또한 행성간 전기장 y성분과 수직방향 TEC 값이 거의 비슷하게 변화하는 것을 볼 수 있었다. 이러한 결과들은 서로 다른 원인에 의해 발생하였지만 전리층의 교란된 전기장이 한반도 상공의 순간적인 TEC 값 증가에 중요한 요인으로 작용함을 보여 준다. By analyzing the observations from a number of ground- and space-based instruments, including ionosonde, magnetometers, and ACE interplanetary data, we examine the response of the ionospheric TEC over Korea during 2003 magnetic storms. We found that the variation of vertical TEC is correlated with the southward turning of the interplanetary magnetic field <TEX>$B_z$</TEX>. It is suggested that the electric fields produced by the dynamo process in the high-latitude region and the prompt penetration in the low- latitude region are responsible for TEC increases. During the June 16 event, dayside TEC values increase more than 15%. And the ionospheric F2-layer peak height (hmF2) was <TEX>${\sim}300km$</TEX> higher and the vertical <TEX>$E{\times}B$</TEX> drift (estimated from ground-based magnetometer equatorial electrojet delta H) showed downward drift, which may be due to the ionospheric disturbance dynamo electric field produced by the large amount of energy dissipation into high-latitude regions. In contrast, during November 20 event, the nightside TEC increases may be due to the prompt penetration westward electric field. The ionospheric F2-layer peak height was below 200km and the vertical <TEX>$E{\times}B$</TEX> drift showed downward drift. Also, a strong correlation is observed between enhanced vertical TEC and enhaaced interplanetary electric field. It is shown that, even though TEC increases are caused by the different processes, the electric field disturbances in the ionosphere play an important role in the variation of TEC over Korea.

Correlation of GSO satellite anomalies with space weather data

This work summarizes the main results of our studies at the ISRO cell of IIT-Mumbai, on the relationship between space weather and geostationary satellite anomalies. We point out that the essence of the problem is to understand quantitatively the relationships between changes in space weather at the Sun (S) and the dayside Lagrangian point (L1) on the one hand, and on the other hand the electron/proton fluxes and magnetic field changes at the geostationary altitude (G). Electromagnetic and cosmic ray changes at the Earth surface (E) are also related to the field and particle changes observed at G. We have evolved prediction programs for satellite anomalies based on proton events on the Sun, the solar wind speeds measured at L1, and the 2MeV electron flux enhancements observed at G. The probabilities and time lags of the occurrence of satellite anomalies are also governed by whether the ‘shock’ in solar wind and IMF parameters detected at L1 is of a ‘sharp’ or a ‘diffuse’ type. From a comparative study of the two years 2005 and 2006 with very different space weather conditions, we find that the type and number of anomalies is (1) clearly governed by the magnitude of the interplanetary electric field Esw, and hence by the IMF B and (2) by the number of proton events on the Sun. We are currently exploring the role played by the ratio of 2MeV electrons to the >1MeV protons, both at G, in the occurrence of satellite anomalies.

Superposed epoch analysis of the dayside ionospheric response to four intense geomagnetic storms

Prompt daytime ionospheric responses are presented for the following four intense geomagnetic storms: 29 October 2003, 30 October 2003, 20 November 2003, and 7 November 2004. We perform a superposed epoch analysis of the storms by defining the start time of the epoch when the Kan‐Lee interplanetary electric field (proportional to the reconnection electric field) first reaches 10 mV/m during a period of continuously southward Bz. Measurements from the GPS receiver onboard the CHAMP satellite at 400 km altitude indicate significant low‐ to middle‐latitude daytime total electron content (TEC) increases above the satellite within 1–2 h of the defined start time for three of the storms (∼1400 local solar time). The 20 November 2003 data follow a different pattern: the largest TEC increases appear several hours (∼5–7) following the interplanetary magnetic field Bz event onset. TEC data obtained from ground‐based GPS receivers for the November 2003 storm tend to confirm a “late” TEC increase for this storm at ∼1400 LT. Estimates of vertical plasma uplift near the equator at Jicamarca longitudes (∼281 E) using the dual‐magnetometer technique suggest that variability of the timing of the TEC response is associated with variability in the prompt penetration of electric fields to low latitudes. It is also found that for the November 2003 magnetic storm the cross‐correlation function between the SYM‐H index and the interplanetary electric field reached maximum correlation with a lag time of 4 h. Such a large lag time has never been noted before. The long delays of both the ionosphere and magnetosphere responses need to be better understood.

Ionosphere disturbances observed throughout Southeast Asia of the superstorm of 20–22 November 2003

Ionospheric disturbances in the Southeast Asian region during the super magnetic storm of 20–22 November 2003 were investigated through an ionosonde chain and a GPS network assisted by the space‐borne instruments. At early stage of the storm in the postsunset sector, large enhancements in the critical frequency of F2 layer and total electron content were observed at northern crest region of the equatorial ionization anomaly (EIA), which might be produced by both the storm meridional wind superimposed with traveling atmospheric disturbances and prompt penetration electric field (PPE). During the main phase of the storm when interplanetary magnetic field started a 12‐h southward turning, equatorial ionosphere was elevated to a very high level which should be most probably caused by a long‐duration PPE event. Meanwhile, at mid‐low latitudes, ionosphere witnessed an initial simultaneous decrease then followed by drastic increases, which is very different from the past observations in this region (Reddy and Nishida, 1992). Combined analysis of the data from the ionosonde and other space‐based measurement shows that for the present case the penetration efficiency of the interplanetary electric field (IEF) to the equatorial ionosphere was larger at night than in the daytime, which agrees with the results of Fejer et al. (2007) showing the ratios of PPE and IEF changes were highly variable with the local time. During the recovery phase, EIA was severely inhibited owing to a wind convergence and possibly because of the westward disturbance dynamo electric field.

Variations in the polar precipitation equatorward boundary during the interaction between the Earth’s magnetosphere and solar wind streams from isolated solar sources

The position of the auroral luminosity equatorward boundary during the interaction between the Earth’s magnetosphere and isolated solar wind streams from different solar sources has been statistically studied based on the ground and satellite observations of auroras. These studies continue the series of the works performed in order to develop the technique for predicting auroras based on the characteristics of the interplanetary medium and auroral disturbances. The dependences of the minimal position of the auroral luminosity equatorward boundary (Φ′) on the values of the azimuthal component of the interplanetary electric field (Ey) and AL indices of magnetic activity, averaged over 6 and 24 h, are presented. The distribution limits for each type of isolated solar wind streams on the Φ′-Ey and Φ′-AL planes have been determined.