Paper on energetic electron precipitation and auroral morphology accepted in JGR

A recent collaborative study between ISEE /Nagoya University and SGO/University of Oulu (+ other institutes) has been accepted to be published in Journal of Geophysical Research: Space Physics, please have a look:

http://onlinelibrary.wiley.com/doi/10.1002/2016JA023484/full

This paper shows a linkage between different auroral morphological structures and the energy spectra of the associated electron precipitation. The study is based on a selected set of case studies combining the EISCAT radar and the KAIRA spectral riometer measurements with the auroral camera observations.

Observation of pulsating aurora signatures in cosmic noise absorption data

A paper was recently accepted for publication in Geophysical Research Letters. It presents the results of a comparison between optical data from an all-sky camera and cosmic noise absorption data measured by KAIRA above Kilpisjärvi, during a pulsating aurora event. 

The accepted version of this article can presently be accessed here; the preliminary reference is:

Grandin, M., A. Kero, N. Partamies, D. McKay, D. Whiter, A. Kozlovsky, and Y. Miyoshi (2017), Observation of pulsating aurora signatures in cosmic noise absorption data, Geophys. Res. Lett., doi:10.1002/2017GL073901.

Abstract
This study investigates the contribution of energetic (E > 30 keV) particle precipitation during a pulsating aurora event over Kilpisjärvi (L = 6.2) on 26 February 2014. It is based on the comparison of auroral blue-line emission (427.8 nm) data from an all-sky camera and cosmic noise absorption (CNA) data obtained from a multi-beam experiment of the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer. The data sets are compared for three KAIRA beams close to magnetic zenith. Results show a clear correlation between the measured CNA and the auroral blue-line emission during the event, for each beam. In addition, individual pulsations are observed for the first time in the CNA data measured by KAIRA, and are found to be close-to-identical to the optical pulsations. This suggests that the modulation of electron precipitation during pulsating aurora takes place in a consistent way over a broad range of energies.

Reply to Comment by Pätzold et al. on “Mars Express radio-occultation data: A novel analysis approach”

A paper was recently accepted for publication in the Journal of Geophysical Research Space Physics. It is a Reply to a Comment on the Grandin et al. (2014) article introducing a new method to analyse radio-occultation data for Mars Express.

The early view of this Reply can be accessed from the Wiley Online Library here.

Grandin, M., P.-L. Blelly, O. Witasse, and A. Marchaudon (2016), Reply to Comment by Pätzold et al. on “Mars Express radio-occultation data: A novel analysis approach”, J. Geophys. Res. Space Physics, 121, doi:10.1002/2015JA022229.

Below is the abstract of the Reply.

We reply to the Comment by Pätzold et al. on our paper presenting a new analysis approach for Mars Express radio-occultation data. We address each of the main comments, showing that none of them invalidates the method itself, but rather, they underline aspects which could be considered to improve the model. One major issue raised by the Comment is the computation of the frequency residual values, as our model did not take into account the change in frequency between the uplink and the downlink. This problem has been given full consideration, and the corresponding part of the model has been corrected accordingly. The dayside profile analyzed in the original article has been reanalyzed with the updated version of the model, and the results are presented, which show overall improvements.

©2016. American Geophysical Union.

Effects of solar wind high-speed streams on the high-latitude ionosphere: Superposed epoch study

Our study of the effects of solar wind high-speed streams on the high-latitude ionosphere, based on data from the SGO ionosonde during the years 2006–2008, has now been accepted for publication. An early-access version is available here, and the reference is:

Grandin, M., A. T. Aikio, A. Kozlovsky, T. Ulich and T. Raita (2015), Effects of solar wind high-speed streams on the high-latitude ionosphere: Superposed epoch study, J. Geophys. Res. Space Physics, 120, doi:10.1002/2015JA021785.

Here is the abstract:

Solar wind high-speed streams (HSSs) are the most important source of geomagnetic disturbances during the declining phase of the solar cycle. Their ionospheric response, especially at high latitudes, is not fully understood yet. We carried out a phase-locked superposed epoch analysis to study the effects of HSSs on the high-latitude ionospheric F region, using data from the Sodankylä ionosonde (L = 5.25) during 2006–2008. We found that the F layer critical frequency f_oF₂ decreases between 12 and 23 magnetic local time (MLT) in summer and around equinoxes for several days. Our interpretation, supported by numerical estimations, is that increased electric fields in the evening sector of the auroral and subauroral regions create ion-neutral frictional heating. Frictional heating will increase the loss rate of O⁺ due to two reasons. The first one is neutral heating producing thermal expansion of the atmosphere and enhancing N₂ and O₂ contents at the F region peak. The second one is ion heating which may occur under strong enough electric fields (about 50–60 mV/m), leading to enhancement of the reaction coefficients. An increase in f_oF₂ is observed in two different MLT sectors. First, a short-lived f_oF₂ increase is visible during all seasons near noon on the first day after the arrival of the HSS, possibly triggered by the compressed solar wind plasma pressure pulse, which may produce particle precipitation from the dayside central plasma sheet. Second, f_oF₂ is enhanced for several days in the morning sector during equinoxes and in winter. We suggest that this is caused by the low-energy tail of particle precipitation.

Variations of foF2 and max(foE, foEs) values compared to background values, by magnetic local time and day number relative to zero epoch. ©2015. American Geophysical Union.