Árpád Kis

Hot flow anomaly remnant in the far geotail

A hot flow anomaly (HFA) like event was observed by the Solar TErrestrial RElations Observatory (STEREO) in the night side magnetosheath in the far tail in February-March 2007. The magnetic signature of the tangential discontinuity was visible, but the resolution of the plasma ion data is not sufficient for our analysis, so a method is given to identify HFAs without solar wind velocity measurements. The event observed in the night side magnetosheath in the far tail might be the remnant of an HFA event, a not-so-active current sheet. This observation suggests that the lifetime of the HFAs might be several 10 minutes, much longer than the expected several minutes.

Increasing the effectiveness of electrical resistivity tomography using γ11n configurations

A new array type, the γ11n arrays are introduced in this paper, in which the sequence of the current(C) and potential (P) electrodes is CPCP and the distance between the last two electrodes is n times the distance between the first two ones and that of the second and third one. These arrays are called quasi null arrays because they are – according to their array and behaviour – between the traditional and null arrays. It is shown by numerical modelling that in detection of small-effect inhomogeneities these configurations may be more effective than the traditional ones including the optimised Stummer configuration. Certain γ11n configurations – especially the γ112, γ113 and γ114 – produced better results both in horizontal and vertical resolution investigations. On the basis of the numerical studies, the γ11n configurations seem to be very promising in problems where the anomalies are similar to the numerically investigated ones, that is they can detect and characterise, for example,tunnels, caves, cables, tubes, abandoned riverbeds or discontinuity in a clay layer with greater efficacy than those of the traditional configurations. γ11n measurements need less data than traditional configurations therefore also the time demand of electrical resistivity tomography (ERT) measurements can be shortened by their use.

Midlatitude ionospheric F2-layer response to eruptive solar events-caused geomagnetic disturbances over Hungary during the maximum of the solar cycle 24: A case study

Abstract In our study we analyze and compare the response and behavior of the ionospheric F2 and of the sporadic E-layer during three strong (i.e., Dst  Mendillo and Narvaez, 2010 ). This way two regular positive phase (RPP) ionospheric storms and one no-positive phase (NPP) storm have been analyzed. In all three cases a significant increase in electron density of the foF2 layer can be observed at dawn/early morning (around 6:00 UT, 07:00 LT). Also we can observe the fade-out of the ionospheric layers at night during the geomagnetically disturbed time periods. Our results suggest that the fade-out effect is not connected to the occurrence of the sporadic E-layers.