Kirsti Kauristie

Bio: Kirsti Kauristie is an academic researcher from Finnish Meteorological Institute. The author has contributed to research in topics: Substorm & Ionosphere. The author has an hindex of 24, co-authored 127 publications receiving 1950 citations.

Ionospheric current signatures of transient plasma sheet flows

Abstract: The plasma flow in the central plasma sheet of the magnetospheric tail often includes short impulsive bursts. Here we investigate the ionospheric signatures of such bursts. The Wind satellite recorded several transient fast flows in the plasma sheet (at geocentric distances of ∼ 12 RE) on December 21–22, 1995. The data are compared with magnetic field observations made in the Scandinavian sector, at the ionospheric conjugate point of the satellite. Superposed epoch analysis of the satellite data suggests that most of the events are Earthward flow bursts accompanied by magnetic dipolarizations, increases in the convection electric field, and drops in the plasma pressure and density. Occasionally, also isolated tailward flow bursts within closed flux tubes can be observed. We demonstrate that in both cases the transient plasma sheet flows are systematically associated with distinct ground magnetic field variations which (after 90° rotation) have specific vortex-like spatial distributions. The vortex patterns have similar duration to that of the flows at Wind and their longitudinal extent (≤1 hour in local time) is consistent with the azimuthal scale sizes (∼3 RE) of the transient flows reported earlier. In many cases the sense of flow rotation observed at Wind and at Wind's ionospheric footpoint agree with our expectation. Despite the care taken in accounting for the instantaneous and local currents that affect the mapping, uncertainties in the footpoint location may still be responsible of the absence of a higher degree for compliance with theory.

Ground-based instruments of the PWING project to investigate dynamics of the inner magnetosphere at subauroral latitudes as a part of the ERG-ground coordinated observation network

Abstract: The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/ ) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (~ 60° geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of dynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics in recent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.

Space weather risk

Abstract: [1] The importance of space weather to society is in a continuous increase since we are more and more dependent on reliable spaceborne and ground-based technological systems. Physical processes involved in space weather constitute a complicated chain from the Sun to the Earth's surface, so the management of space weather risks requires expertise in many disciplines of science and technology. In this paper, geomagnetically induced currents in electric power networks are considered in detail, referring particularly to research carried out in Finland. Today's monitoring systems of natural risks, such as floods and forest fires, are based on satellite observations. Spacecraft and communication between satellites and the ground are vulnerable to space weather. Thus, besides being a direct risk to technology, space weather may also indirectly have adverse effects on risk management. European efforts, which take into account both aspects, are also discussed in this paper.

What can we tell about global auroral-electrojet activity from a single meridional magnetometer chain?

Abstract: The AE indices are generally used for monitoring the level of magnetic activity in the auroral oval region. In some cases, however, the oval is either so expanded or contracted that the latitudinal coverage of the AE magnetometer chain is not adequate. Then, a longitudinal chain in the key region would give more information of the real situation, but, of course, only during some limited UT-period. In order to find out the UT coverage of a single meridional chain, we have compared the global AL and AU indices with corresponding local indices determined using data from the meridional part of the EISCAT Magnetometer Cross during the years 1985?1987. A statistical study shows that the local indices are close (within relative error of 0.2) to the global AU and AL during periods 1500?2000 UT (~1730?2230 MLT) and 2130?0130 UT (~0000?0400 MLT), respectively. In the middle of these optimal MLT-sectors the EISCAT Cross sees more than 70% of the cases when the global AE chain records activity. Then, also the correlation between the local and global indices is generally good (>0.7). Thus we conclude that five to six evenly located meridional chains are needed for covering all the UT-periods. On the other hand, already the combination of IMAGE, CANOPUS, and the Greenland chains catches ~50% of the substorms. Case-studies show that usually during 2130?1100 UT the AL achieved from these chains reproduces the real AL with good timing, although it does not follow all transient variations.

Neutral line model of substorms: Past results and present view

Abstract: The near-Earth neutral line (NENL) model of magnetospheric substorms is reviewed. The observed phenomenology of substorms is discussed including the role of coupling with the solar wind and interplanetary magnetic field, the growth phase sequence, the expansion phase (and onset), and the recovery phase. New observations and modeling results are put into the context of the prior model framework. Significant issues and concerns about the shortcomings of the NENL model are addressed. Such issues as ionosphere-tail coupling, large-scale mapping, onset trigger- ing, and observational timing are discussed. It is concluded that the NENL model is evolving and being improved so as to include new observations and theoretical insights. More work is clearly required in order to incorporate fully the complete set of ionospheric, near-tail, midtail, and deep- tail features of substorms. Nonetheless, the NENL model still seems to provide the best avail- able framework for ordering the complex, global manifestations of substorms.

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

Abstract: The Super Dual Auroral Radar Network (SuperDARN) has been operating as an international co-operative organization for over 10 years. The network has now grown so that the fields of view of its 18 radars cover the majority of the northern and southern hemisphere polar ionospheres. SuperDARN has been successful in addressing a wide range of scientific questions concerning processes in the magnetosphere, ionosphere, thermosphere, and mesosphere, as well as general plasma physics questions. We commence this paper with a historical introduction to SuperDARN. Following this, we review the science performed by SuperDARN over the last 10 years covering the areas of ionospheric convection, field-aligned currents, magnetic reconnection, substorms, MHD waves, the neutral atmosphere, and E-region ionospheric irregularities. In addition, we provide an up-to-date description of the current network, as well as the analysis techniques available for use with the data from the radars. We conclude the paper with a discussion of the future of SuperDARN, its expansion, and new science opportunities.

「Earth,Planets and Space」のオープンアクセス出版

Abstract: ▶ Gathers original articles on topics in earth and planetary sciences ▶ Coverage includes geomagnetism, aeronomy, space science, seismology, volcanology, geodesy and planetary science ▶ Official journal of the Society of Geomagnetism and Earth, Planetary and Space Sciences, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan, and The Japanese Society for Planetary Sciences

The Effects of Geomagnetic Disturbances on Electrical Systems at the Earth's Surface - An Update

Abstract: Abstract Geomagnetic disturbances have affected electrical systems on the ground for over 150 years. The first effects were noted on the early telegraph in the 1840s and in this century magnetic storms have caused power system blackouts and phone system outages. Affected systems include all those that use electrical conductors: whether for transmission of power or signals or where the conducting properties are incidental to their use such as with pipelines and railway tracks. In power systems geomagnetically induced currents cause partial saturation of power transformers producing transformer heating and distortion of the ac waveform leading to misoperation of relays and other equipment. On pipelines, induced currents may contribute to corrosion but also present a problem with the electrical surveys of the pipe performed to monitor the corrosion prevention systems. Severity of these effects depends on disturbance size, proximity to the auroral zone, and the conductivity structure of the Earth. Also significant are system parameters such as the use of higher resistance coatings on pipelines and the linking of power systems into larger networks. In this paper we have attempted to catalogue all the published reports of geomagnetic effects on electrical systems and show their occurrence in the context of the solar cycle and geomagnetic activity variations for the years 1844 to 1996.

Substorm onset observations by IMAGE-FUV

Abstract: [1] Over the first 2.5 years of operation, the FUV instrument on the IMAGE spacecraft observed more than 2400 substorm onsets in the Northern Hemisphere. The observations confirm earlier results of statistical studies in terms of a median substorm onset location at 2300 hours MLT and 66.4 degrees magnetic latitude. The purpose of this report is to publish the list to allow for further investigation. The list can easily be searched for onsets close to certain ground stations or at specific magnetic latitudes or local times. As one example of such use, we demonstrate how the probability of onset observation was determined for the ground-based automatic observatories of the THEMIS (Time History of Events and Macroscale Interactions during Substorms) project.