Moderate Geomagnetic Activity Research Articles

STEVE Events With FUV Emissions

AbstractSTEVE, Strong Thermal Emission Velocity Enhancement, was often observed by ground‐based imagers in visible wavelengths and rarely detected by global FUV imagers. We present a new event, and revisit two reported STEVE events, that were observed by the DMSP/SSUSI FUV imager at O 135.6 nm, N2 LBHS, and LBHL emissions. Coincident particle and plasma drift observations showed that the events were associated with high ion drift speed, low ion density and no energetic particle precipitation. This is consistent with earlier findings (e.g., MacDonald et al., 2018, https://doi.org/10.1126/sciadv.aaq0030; Gallardo‐Lacourt et al., 2018a, https://doi.org/10.1029/2018ja025368, 2018b, https://doi.org/10.1029/2018gl078509; Archer et al., 2019). In this paper, several new features are identified: (a) Detection rates of FUV STEVE are much lower than that of visible STEVE; (b) The STEVE on 27 March 2008 covers 3‐hr local time with a length up to 2,700 km around 60° magnetic latitudes; (c) Different widths of STEVE observed in O 135.6 nm and N2 LBH images indicate a large altitude range in the STEVE FUV emissions; (d) The true ion (assuming O+) drift speeds during the 27 March 2008 STEVE event could be up to 20 km/s, well above the DMSP SSIES sensor limit. The kinetic energy of the high speed ions is larger than the excitation potential of the observed FUV emissions; (e) The requirement of such extreme high ion drift speed explains why FUV STEVE have been rarely observed, compared to the visible STEVE; (f) The three FUV STEVE events occurred during moderate geomagnetic activity; (g) Theses events were conjugate in both hemispheres.

Assessing the performance of IRI-2016 and IRI-2020 models using COSMIC-2 GNSS radio occultation TEC data under different magnetic activities over Egypt

Abstract Variations in Total Electron Content (TEC) between the COSMIC-2, IRI-2016, and IRI-2020 are considered under different levels of geomagnetic storm activity: minor, moderate, and severe. TEC values are scrutinized at three levels of the Kp index, which serves as a metric for gauging the strength of a magnetic storm (Kp = 3.0, Kp = 6.0, Kp = 8.0) and across four-time intervals throughout 24 h to understand the performance of the models during both day and night-time conditions. Statistical analysis reveals that the standard deviation of TEC variations is lower during minor storms than moderate and severe. The comparison of variations between COSMIC-2 Radio Occultation TEC and both IRI-2016 and IRI-2020 models revealed more substantial discrepancies during day-time intervals; This was likely attributed to the dynamic and complex nature of the ionosphere influenced by solar radiation and other factors. Comparative analysis across the three levels of storm activity demonstrated that IRI2020 provided improved results over IRI2016, particularly during minor geomagnetic storm events. The study demonstrates that IRI2020 is more accurate than IRI-2016 at forecasting ionospheric conditions, especially at night and during moderate geomagnetic storm activity periods. Both models, however, provide valuable insights during challenging space weather conditions, and the results demonstrate their utility in understanding and forecasting the ionosphere’s behavior. The results yield valuable insights into space weather conditions and their effects on technology and communication, highlighting the potential for further improvement in TEC prediction models.

Classification and Distribution of the Dayside Ion Upflows Associated with Auroral Particle Precipitation

Two important phenomena of the solar wind–magnetosphere–ionosphere coupling are auroral particle precipitation and the formation of ions flowing upward from the ionosphere. They have opposite transport directions of energy and substance. Based on the observations of particle precipitation and ion drift from the DMSP F13 satellite in January and July 2005, the ionospheric ion upflows in dayside auroral oval (0600–1800 MLT) can be divided into five types according to the velocity of ion upflows and the spectrum characteristics of auroral particle precipitation, and the distribution for different types of ion upflows is studied. The results show that the ion upflows mainly occur in the geomagnetic latitude (MLAT) range of 70–80°.The main magnetospheric source region of ion upflows (type A and D) caused by the accelerated electron (mainly the soft electron) corresponds to Low Latitude Boundary Layer (LLBL) and Cusp, and ion upflows of type B and C (related to the process of ambipolar diffusion caused by electron acceleration) mainly occur in LLBL and Boundary Plasma Sheet (BPS), while ion upflows of type E without electron acceleration mainly occur in the central plasma sheet (CPS).The dawn–dusk asymmetry is obvious in the winter season, with the ion upflows mainly occurring on the dawn/dusk side ionosphere. However, the ion upflows in summer mainly occur at the magnetic noon, with a symmetric distribution centered at the magnetic noon. The occurrence of ion upflow in winter is significantly higher than that in summer, and it is significantly enhanced during the period of moderate geomagnetic activity. The upward region expands to the lower latitude when the geomagnetic activity is enhanced. The effect of interplanetary magnetic field (IMF) components has also been studied in this paper. When IMF Bx is negative, the upflow occurrence increases in the region of 1500–1800 MLT and 0600–0900 MLT, with the MLAT range below 70°. The direction of IMF By may lead to the high-incidence area reverse at the prenoon or postnoon region. The occurrence of ion upflows with the MLAT range below 75° increases significantly when IMF is southward. Type A ion upflow has the highest velocity of ion upflows, followed by type E, and type D has the lowest. The average velocity of ion upflows in winter is significantly higher than that in summer.

Ionospheric Semidiurnal Lunitidal Perturbations During the 2021 Sudden Stratospheric Warming Event: Latitudinal and Inter‐Hemispheric Variations in the American, Asian‐Australian, and African‐European Sectors

AbstractThe ionosphere exhibits enhanced semidiurnal lunitidal (M2) perturbations during sudden stratospheric warming (SSW) events, of which the manifestation and mechanism are not well documented and understood. This paper studies the latitudinal and inter‐hemispheric variations of the ionospheric M2 perturbations during the 2021 major Arctic SSW with total electron content (TEC) data in the American, Asian‐Australian, and African‐European sectors. Results show that the M2 perturbations in the three sectors all enhanced during the SSW, with the strongest M2 perturbations in the Northern and Southern Hemispheres at about 10°∼15°N and 25°∼30°S geomagnetic latitudes, respectively. Also, clear M2 perturbations in the three sectors all extended to middle latitudes during the SSW only in the Southern Hemisphere. Comparatively, the inter‐hemispheric asymmetry of the magnitude of the M2 perturbations during the SSW was more complex. The inter‐hemispheric asymmetry of the crest locations of the low‐latitude M2 perturbations in the three sectors during the SSW was probably due to the F‐region meridional wind effect on the diffusion process of the low‐latitude plasma fountain. Meanwhile, the longitudinal differences were also obvious. The TEC M2 amplitude in the American sector was obviously larger than those in the Asian‐Australian and African‐European sectors during the SSW. The M2 characteristics in the southern middle latitude in the American sector were significantly different from those in the other two sectors during the SSW, which may be related to the differences of the combined effects of the local wind and geomagnetic configuration. In addition, a moderate geomagnetic activity occurred during the 2021 SSW, which brings difficulties to the analysis of the SSW‐related TEC variation.

Statistical study and corresponding evolution of plasmaspheric plumes under different levels of geomagnetic storms

Abstract. Using observations of Van Allen Probes, we present a statistical study of plasmaspheric plumes in the inner magnetosphere. Plasmaspheric plumes tend to occur during the recovery phase of geomagnetic storms. Furthermore, the results imply that the occurrence rate of observed plasmaspheric plume in the inner magnetosphere is larger during stronger geomagnetic activity. This statistical result is different from the observations of the Cluster satellite with much higher L shells in most orbital periods, which suggests that the plasmaspheric plume near the magnetopause tends to be observed during moderate geomagnetic activity (Lee et al., 2016). In the following, the dynamic evolutions of plasmaspheric plumes during a moderate geomagnetic storm in February 2013 and a strong geomagnetic storm in May 2013 are simulated through group test particle simulation. It is obvious that the plasmaspheric particles drift out on open convection paths due to sunward convection during both geomagnetic storms. It seems that the outer plasmaspheric particles exhaust the energy available to them sooner, and the plasmasphere shrinks faster during strong geomagnetic storms. As a result, the longitudinal width of the plume is narrower, and the plume is limited to lower L shells during the recovery phase of strong geomagnetic storm. The simulated evolutions may provide a possible interpretation for the occurrence rates: Van Allen Probes tend to observe plumes during stronger geomagnetic storms, and the Cluster satellite with higher L shells tends to observe plumes during moderate geomagnetic storms.

Ionospheric Disturbances Observed Following the Ridgecrest Earthquake of 4 July 2019 in California, USA

Earthquakes are known to generate disturbances in the ionosphere. Such disturbances, referred to as co-seismic ionospheric disturbances, or ionoquakes, were previously reported for large earthquakes with magnitudes Mw≥ 6.6. This paper reports ionoquakes associated with the Ridgecrest earthquakes of magnitude (Mw=6.4), that occurred on 4 July 2019 in California, USA. The ionoquakes manifested in total electron content (TEC) in the form of traveling ionospheric disturbances (TIDs) within 1 h from the mainshock onset. These seismic-origin TIDs have unique wave characteristics that distinguish them from TIDs of non-seismic origin arising from a moderate geomagnetic activity on the same day. Moreover, in the space-time domain of the detection of seismic-origin TIDs, TIDs are absent on the day before and day after the earthquake day. Their spectral characteristics relate them to the Earth’s normal modes and atmospheric resonance modes. We found the ground velocity associated with the mainshock, rather than the ground displacement, satisfies the threshold criteria for detectable ionoquakes in TEC measurements. Numerical simulation suggested that the coupled seismo–atmosphere–ionosphere (SAI) dynamics energized by the atmospheric waves are responsible for the generation of ionoquakes. This study’s findings demonstrate the potential of using TEC measurement to detect the ionospheric counterparts of moderate earthquakes.

Statistics on Omega Band Properties and Related Geomagnetic Variations

AbstractUsing the list of the omega structures based on the Magnetometers‐Ionospheric Radars‐All‐sky Cameras Large Experiment network (Partamies et al., 2017, https://doi.org/10.5194/angeo-35-1069-2017), we obtained a number of important statistical characteristics describing the surface magnetic field. Based on 438 events, typical magnetic variations associated with the passage of the single omega were obtained. The typical variation, obtained using superposed epoch analysis, is associated with a local bending of the westward electrojet and statistically confirms the distribution of equivalent ionospheric currents obtained in earlier observations of single omegas. It was found that during low and moderate geomagnetic activity, the appearance of the omega structures in the dark morning magnetic local time (MLT) sector results in two times higher than average dB/dt on the ground surface. Also, the velocity, direction of movement, and area of omega structures were calculated. It is shown that faster and bigger omegas produce larger time derivatives of the ground magnetic field. Furthermore, we demonstrate that in the 03–08 MLT sector, superposed magnetic variations for the arbitrary events of very high time derivatives |dB/dt| > 10 nT/s, reveal magnetic signatures similar to omegas. Our findings, together with the results described by Apatenkov et al. (2020, https://doi.org/10.1029/2019gl086677), emphasize the important role of omega structures in the formation of large geomagnetically induced currents.

Van Allen Belt Punctures and Their Correlation With Solar Wind, Geomagnetic Activity, and ULF Waves

AbstractWe investigate the rare events of sudden appearances of relativistic electrons (>700 keV), which are normally confined to the Van Allen belts, in the slot region. The frequency of occurrence of these events is on average 1–2 per year. To cope with the scarcity of events, in this study, we examine 21 years of trapped relativistic electron fluxes available from the POES and MetOp Space Environment Monitor (SEM‐2). Our statistical analysis shows that these events can occur even during moderate geomagnetic activity. Occurrence of these events correlates with high‐speed solar winds or interplanetary coronal mass ejections depending on the phase of the solar cycle. A strong correlation of these events is found with ultra‐low frequency (ULF) wave activity, which can be used to predict these events with more than 75% accuracy.

A stress test to evaluate the usefulness of Akaike information criterion in short-term earthquake prediction

Akaike information criterion (AIC) has been recently adopted to identify possible earthquake precursors in ionospheric total electron content (TEC). According to the authors of this methodology, their technique allows finding abrupt increases (positive breaks) in vertical TEC rate of change 25–80 min before the occurrence of large earthquakes, highlighting a promising implication of AIC method in Mw > 8 earthquakes alert strategies. Due to the relevance of this matter, a lively scientific debate ensued from these results. In this study, we carefully evaluate AIC method potentiality in searching earthquake TEC precursory signatures. We first investigate the dependence of the detected breaks number on the adjustable AIC method parameters. Then, we show that breaks occurrence clusters around specific local times and around moderate and high solar and geomagnetic activity. The outcome of this study is that AIC method is not concretely usable for issuing large earthquakes alerts.

Recurrent Galactic Cosmic-Ray Flux Modulation in L1 and Geomagnetic Activity during the Declining Phase of the Solar Cycle 24

Abstract Short-term variations (<1 month) of the galactic cosmic-ray (GCR) flux in the inner heliosphere are mainly associated with the passage of high-speed solar wind streams (HSS) and interplanetary (IP) counterparts of coronal mass ejections (ICMEs). Data gathered with a particle detector flown on board the ESA LISA Pathfinder (LPF) spacecraft, during the declining part of solar cycle 24 (2016 February–2017 July) around the Lagrange point L1, have allowed us to study the characteristics of recurrent cosmic-ray flux modulations above 70 MeV n−1. It is shown that the amplitude and evolution of individual modulations depend in a unique way on both IP plasma parameters and particle flux intensity before HSS and ICME transit. By comparing the LPF data with those gathered contemporaneously with the magnetic spectrometer experiment AMS-02 on board the International Space Station and with those of Earth’s polar neutron monitors, the GCR flux modulation was studied at different energies during recurrent short-term variations. It is also aimed to set the near real-time particle observation requirements to disentangle the role of long- and short-term variations of the GCR flux to evaluate the performance of high-sensitivity instruments in space such as the future interferometers for gravitational wave detection. Finally, the association between recurrent GCR flux variation observations in L1 and weak to moderate geomagnetic activity in 2016–2017 is discussed. Short-term recurrent GCR flux variations are good proxies of recurrent geomagnetic activity when the B z component of the IP magnetic field is directed north.

Longitudinal Variation of the Ionospheric Response to the 26 August 2018 Geomagnetic Storm at Equatorial/Low Latitudes

We have studied the ionospheric response at near-equator latitudes during the geomagnetic storm of 26 August 2018, which was the strongest geomagnetic disturbance that year (minimum Dst value: −174 nT). For the analysis, we considered the F2-layer critical frequency (foF2) and peak height (hmF2), as well as total electron content (TEC) data for Jicamarca (geographic coordinates: 12° S, 283.2° E; geomagnetic coordinates: 2.26° S, 4.09° W), Saoluis (geographic coordinates: 2.6° S, 315.8° E; geomagnetic coordinates: 5.94° N, 28.5° E), Guam (geographic coordinates: 13.4° N, 144.8° E; geomagnetic coordinates: 5.73° N, 143.2° W) and Libreville (geographic coordinates: 0.39° N, 9.45° E; geomagnetic coordinates: 1.64° N, 82.6° W). First, we observed pre-storm improvements, which could be due to previous moderate geomagnetic activity. Second, only one station (Jicamarca) clearly revealed a prompt penetration electric field (PPEF) effect when Bz turned strongly negative during the initial phase of the storm. Over the stations Saoluis and Guam, a PPEF effect was not evident. These stations presented pre-storm enhancements in foF2. In this case study, disturbed dynamo electric fields appear not to have played a crucial role in increasing electron density near equatorial regions during the recovery phase because the observed disturbances did not correspond with those produced by these electric fields, that is, negative (positive) storm effects on the dayside (night). Third, the increases in electron density observed during recovery are most likely caused by neutral composition changes.

Concurrent Observations Of Magnetic Reconnection From Cluster, IMAGE and SuperDARN: A Comparison Of Reconnection Rates And Energy Conversion

AbstractAuroral emissions reflect energy dissipation in the atmosphere, while the energy mostly originates from the magnetospheric dynamics of the planet. In the Earth's magnetosphere, the interaction between the solar wind and the terrestrial magnetic field produces magnetic reconnection ultimately causing the appearance of auroras in the polar regions. In this study, we revisit two reconnection events previously identified using ESA Cluster observations during conditions of moderate geomagnetic activity, in the magnetotail. We compare these in situ detections with simultaneous global auroral images from the NASA‐IMAGE satellite and ionospheric convection measurements from SuperDARN. We show for the first time a direct correspondence between the electric voltage estimated at ionospheric altitude and the reconnection rate at the reconnection site. We compute the total auroral precipitation power and compare it to the energy released from the reconnection site. We deduce that the precipitated electron power of the aurora and the electron energy deposition rate from the reconnection site are of the same order of magnitude, which means that the thermal energy released by reconnection is primarily transferred to the ionosphere and contributes to the auroral activity.

Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes

AbstractWe present a statistical analysis with 100% duty cycle and non‐time‐averaged amplitudes of the prevalence and distribution of high‐amplitude >50‐pT whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Whistler mode waves with high magnetic field amplitudes are most common above L=4.5 and between magnetic local time of 0–14 where they are present approximately 1–6% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 25% in some regions. The dayside population are more common during quiet or moderate geomagnetic activity and occur primarily >5° from the magnetic equator, while the night‐to‐dawn population are enhanced during active times and are primarily within 5° of the magnetic equator. These results are different from the distribution of electric field peaks discussed in our previous paper covering the same time period and spatial range. Our previous study found large‐amplitude electric field peaks were common down to L=3.5 and were largely absent from afternoon and near noon. The different distribution of large electric and magnetic field amplitudes implies that the low‐L component of whistler mode waves observed previously are primarily highly oblique, while the dayside and high‐L populations are primarily field aligned. These results have important implications for modeling radiation belt particle interactions with chorus, as large‐amplitude waves interact nonlinearly with electrons, resulting in rapid energization, de‐energization, or pitch angle scattering. This also may provide clues regarding the mechanisms which can cause significant whistler mode wave growth up to more than 100 times the average wave amplitude.

Исследование сезонных особенностей формирования областей повышения электронной температуры в субавроральной ионосфере

The electron temperature enhancement is known to occur in the main ionospheric trough during geomagnetic disturbances. In this paper, we study fea-tures of the formation of the electron temperature (Te) enhancement in the subauroral ionosphere by comparing results of the numerical simulation with measurements of Te onboard the CHAMP satellite under moderate geomagnetic activity conditions. It is shown that depending on the terminator position and universal time (UT), the location of the enhanced Te regions in the subauroral ionosphere varies in different seasons. So, in winter ring-shaped and sickle-shaped regions can be formed, whereas during the equinox and summer periods sickle-shaped regions of different lengths and clarity are generally observed.

Investigating seasonal features of electron temperature enhancement regions in the subauroral ionosphere

The electron temperature enhancement is known to occur in the main ionospheric trough during geomagnetic disturbances. In this paper, we study fea-tures of the formation of the electron temperature (Te) enhancement in the subauroral ionosphere by comparing results of the numerical simulation with measurements of Te onboard the CHAMP satellite under moderate geomagnetic activity conditions. It is shown that depending on the terminator position and universal time (UT), the location of the enhanced Te regions in the subauroral ionosphere varies in different seasons. So, in winter ring-shaped and sickle-shaped regions can be formed, whereas during the equinox and summer periods sickle-shaped regions of different lengths and clarity are generally observed.

Modeling the electron temperature distribution in F2 region of high-latitude ionosphere for winter solstice conditions

Using the three-dimensional model of the high-latitude ionosphere in Euler variables, which takes into account the mismatch between geographic and geomagnetic poles, we study the behavior of the electron temperature Te in the F2 region as a function of universal time. We present results of the numerical modeling of spatial-temporal distribution of electron temperature in the F2 region for winter solstice, minimum solar activity, and moderate geomagnetic activity. The electron temperature distribution in the F2 region of the high-latitude ionosphere in winter is shown to be characterized by a Te increase in dawn and dusk sectors. Further, the mismatch between the poles leads to regular longitudinal features in Te distribution during Earth’s daily rotation. Thus, at 05 UT, when the Eastern Hemisphere is illuminated, the elevated Te zone is formed only in the dawn sector, and at 17 UT, when the Western Hemisphere is illuminated such zones are observed in both the sectors. We discuss reasons for the formation of the regions with elevated electron temperature depending on the universal time. Results of numerical experiments are compared with similar results obtained with other models.

Моделирование распределения температуры электронов в области F2 высокоширотной ионосферы для условий зимнего солнцестояния

Using the three-dimensional model of the high-latitude ionosphere in Euler variables, which takes into account the mismatch between geographical and geomagnetic poles, we study the behavior of the electron temperature Te in the F2 region as a function of universal time. We present results of the numerical modeling of spatial-temporal distribution of electron temperature in the F2 region for winter solstice, minimum solar activity, and moderate geomagnetic activity. The electron temperature distribution in the F2 region of the high-latitude ionosphere in winter is shown to be characterized by a Te increase in dawn and dusk sectors. Further, the mismatch between the poles leads to regular longitudinal features in Te distribution during Earth’s daily rotation. Thus, at 05 UT, when the Eastern Hemisphere is illuminated, the elevated Te zone is formed only in the dawn sector, and at 17 UT, when the Western Hemisphere is illuminated, such zones are observed in both the sectors. We discuss reasons for the formation of the regions with elevated electron temperature depending on the universal time. The results of numerical experiments are compared with similar results obtained with other models.

A statistical study of plasmaspheric plumes and ionospheric outflows observed at the dayside magnetopause

AbstractWe present a statistical study of plasmaspheric plumes and ionospheric outflows observed by the Cluster spacecraft near the dayside magnetopause. Plasmaspheric plumes are identified when the low‐energy ions (<1 keV) with ∼90° pitch angle distributions are observed by the Cluster Ion Spectrometer/Hot Ion Analyzer instrument. The ionospheric outflows are characterized by unidirectional or bidirectional field‐aligned pitch angle distributions of low‐energy ions observed in the dayside magnetosphere. Forty‐three (10%) plasmaspheric plume events and 32 (7%) ionospheric outflow events were detected out of the 442 times that C3 crossed the dayside magnetopause between 2007 and 2009. The occurrence rate of plumes at duskside is significantly higher than that at dawnside. The occurrence rate of outflows shows a weak dawn‐dusk asymmetry. We investigate the dependence of the occurrence rates of plumes and ionospheric outflows on geomagnetic activity and on solar wind/interplanetary magnetic field (IMF) conditions. The plume events tend to occur during southward IMF (duskward solar wind electric field) and moderate geomagnetic activity (Kp = 3,−30≤Dst <− 10 nT). However, the ionospheric outflow events tend to occur during northward IMF (dawnward solar wind electric field). The ionospheric outflows do not occur when Kp = 0, and the occurrence rate of the ionospheric outflows does not have a clear Dst dependence. Seventy‐five percent (46%) of the outflows are observed in the duskside for negative (positive) IMF By. Conversely, 54% (25%) of the outflows are observed in the dawnside for positive (negative) IMF By. Finally, the occurrence rates of both plumes and outflows increase with solar wind dynamic pressure.

Geomagnetic (MIE) and storm sudden commencement (SSC) impulses in a high-latitude magnetosphere

Amplitude regularities, intermittence statistics, and conditions of generation of magnetic (mag- netic impulse event, MIE) and geomagnetic storm sudden commencement (SSC) impulses were compara- tively analyzed. Common and different properties of MIE and SSC impulses observed in a high-latitude mag- netosphere were detected. It was shown that MIE impulses are observed against a background of relatively stable interplanetary medium parameters and mostly when the IMF sector structure is negative. SSC impulses are observed against a background of sharply increasing solar wind and IMF parameters and when the IMF sector structure is positive. The amplitude dynamics, depending on the geomagnetic latitude of MIE and SSC impulses relative to the noon meridian, as well as in the daytime and nighttime MLT sectors, is sim- ilar. The dynamics of the intermittence indices (α), depending on the geomagnetic latitude of MIE and SSC impulses in the same MLT sectors, is antiphase. Independently of the IMF sector structure, the amplitudes of MIE and SSC impulses increase with increasing geomagnetic latitude, and the intermittence indices change in antiphase. It is assumed that the degree of plasma turbulence at the front boundary of magneto- sphere at moderate geomagnetic activity is relatively high and sufficient for the generation of MIE impulsive regimes. At the same time, SSC impulses originate at a lower turbulence level in the subsolar magnetospheric region but under the external action of solar wind inhomogeneities on the magnetosphere.

Recovering of local magnetic K-indices from global magnetic Kp-indices using neural networks: an application to Antarctica

<p>This paper describes a method to obtain local magnetic index, K, from the global index, Kp. Until now, however, for the cases of areas without magnetic observatories, to estimate the geomagnetic activity there, global indices were the only option. The methodology that we used to estimate local index was based on neural networks. This tool has a great potential for processing information from complex systems as in the case of the geomagnetic system. Local K index calculated with this method resulted to be a better option than directly using the global index Kp when we need an indicator of geomagnetic activity in a specific area. The best results of our method were for moderate and high geomagnetic activity, which are of major interest in Space Weather.</p>