Plenary - Space Weather in planetary systems

Gaël Cessateur - Alexander Shapiro - Mathieu Barthélémy
Wednesday 20/11, 09:00 - 10:30 and 11:00 - 12:30

Stellar and Solar irradiance are the main external forcing on planetary atmospheres and also strongly impact the space environment. Stellar and Solar activity triggers the local space weather conditions, so it is a primary input for modellers. Although measurements and modeling of the solar irradiance were under close attention during the last decade, the complete picture of solar variability and its impact on climate is still far from being clear. In particular, the secular component of solar variability is poorly understood, mainly because long-term measurements are scarce. Nevertheless, there is a rich set of observational data of Sun-like stars collected from the ground (i.e. APT measurements at Fairborn Observatory) and space (i.e. Kepler or Corot). Comparison of solar and stellar data should allow us to better understand and constrain the solar and stellar variability at all time scale (from flares to secular variations), which is relevant both for the Earth's climate and the habitability and detectability of extrasolar planets. This session invites contributions concerning all aspects of solar and stellar variability, especially emphasizing on what both communities can learn from each other. We also welcome contributions devoted to the interaction between planetary atmospheres and the Stellar/Solar flux in order to find out which tools might be used in the future for detecting Earth-like extrasolar planets.

Oral contributions

Seq   Time   Title
1   09:00   A Generic Description of Planetary Aurora
De Keyser, Johan; Maggiolo, Romain; Maes, Lukas
Belgian Institute for Space Aeronomy, BELGIUM

A comparative study of the magnetospheres of the planets in our own Solar System helps to gain insight into the generic mechanisms that drive aurora. In this discussion, we will limit ourselves to quasi-static aurora. Even a relatively simple model is able to describe the variety of auroral generators found in the Earths magnetosphere, but also in that of the gas giants. From current continuity one can infer a number of properties of the auroral circuit, of the particle precipitation associated with it, and also of the resulting ionospheric outflow. The auroral emissions are further determined by the composition of the ionosphere of the planet. We will propose a classification of different types of magnetised planets and explain how their properties determine the nature of the auroras that can be expected. Auroral emission may, eventually, be detected in exoplanet atmospheres and in such cases it would provide information on atmospheric composition.

2   09:20   Airglow and Auroral Emission from Ganymede
Barthelemy, Mathieu1; Cessateur, Gael2; Abisset, Antoine3
2Physikalisch-Meteorilogisches Observatorium Davos / World Radiation Center, SWITZERLAND;

In term of space environment Ganymede is a unique object in the solar system. Its own magnetic field in the jovian magnetosphere gives rise to particles precipitation. Although these object have a very faint atmosphere, their exosphere can show some emissions features due to both solar UV flux and precipitating particles. We recently calculated the effects of the solar UV flux (Cessateur et al 2012). However, in the case of the polar region of Ganymede the precipitating electrons play an important role in the emission features as measured by Hall et al. (1997) and Feldman (2000) for the O 130 nm triplet. To calculate these emissions, we use the atmospheric model produced by Marconi (2007). We use a simple primary ionization calculation. This is justified by the fact that the atmosphere is essentially non collisionnal except at very low altitudes and latitudes.For the solar UV flux, we used the configuration already explained in Cessateur et al. (2012). For the electrons, we used several type of spectrum. By comparison between the data of Feldman et al., we hope to constraint the electrons fluxes precipitating in the atmosphere of Ganymede. These calculations give strong information on the processes involved in the Ganymede environment. In particular, we will be able to produce constraints on the electrons spectrum precipitating in Ganymede atmosphere.

3   09:50   Satellite Retrieved Cloud Data Limitations and the Evaluation of a Solar - Cloud Llink
Calogovic, Jasa
Faculty of Geodesy, CROATIA

A hypothesized link between the solar-modulated cosmic ray (CR) flux and the Earth's cloud properties is still the subject of intense debate. Numerous authors have examined a hypothesized link between CR and clouds during Forbush decrease events using daily timescale epoch-superpositional (composite) methods. However, such studies have arrived at a range of conflicting results. Using extensive Monte Carlo simulation techniques, we demonstrate that for the two most widely used satellite cloud datasets, the International Satellite Cloud Climatology Project (ISCCP) and the MODerate Resolution Imaging Spectroradiometer (MODIS), high noise levels present in composites of small sample sizes or and/or overly isolated sample areas, coupled with incorrect methods of assessing significance may account for the inconsistent results. From our quantification of sample uncertainty we review some of the important investigations which have claimed to identify a significant solar - cloud link, and conclude that no strong evidence to support this hypothesis has yet been identified from satellite observations.

4   10:10   Longterm Reconstruction of the Solar EUV for Planetary Science Applications
Haberreiter, Margit1; Beer, Jürg2; Delouille, Veronique3; Mampaey, Benjamin3; Verbeeck, Cis3; Schmutz, Werner1

Variations of the solar irradiance determine the temperature, density, and composition of any planetary atmosphere. For our understanding of the longterm changes of planetary atmospheres it is important to be able to provide realistic variations of the EUV. Here, we present first preliminary results of the longterm reconstruction of the solar EUV since 1610. This work is based on the one hand on segmentation maps of EIT images for the SOHO era. Synthetic spectra, emitted by the identified coronal features, are weighted by the filling factors derived from the segmentation maps, yielding the variations of the EUV for Solar Cycle 23. Moreover, for the reconstruction of the EUV since the Maunder Minimum we use the cosmogenic isotopes determined from ice cores along with the Sunspot number and neutron monitor data following the approach by Shapiro et al., 2011. The results will be compared to existing EUV reconstructions and their potential for planetary applications will be outlined.

5   11:00   Where and how much is Solar Irradiance increasing during Flare ?
Kretzschmar, Matthieu
LPC2E, CNRS & University of Orléans, FRANCE

Solar and stellar flares impact the atmosphere of planets through electromagnetic radiation and particles. The lack of simultaneous observations at all wavelengths as well as very different contrasts over the spectrum make the spectral distribution of the flare energy still poorly known, while it is essential for characterizing their impact on planetary atmospheres. In this study, we will use different datasets to address this question. In particular, we will present a statistical analysis of solar flares observed by the EUV variability experiment (EVE) onboard SDO and quantify the energy released at various wavelength relevant for space weather. Our results suggest that most of the flare energy goes into the visible range as well as at very short wavelengths.

6   11:25   What is the Contribution of Different Magnetic Structures to the Solar Spectral Irradiance Variability?
Vuets, Anatoly; Dudok de Wit, Thierry; Kretzschmar, Matthieu

The solar radiative output in the UV and Extreme-UV (EUV) is a crucial quantity for space weather applications that require a specification of the thermosphere/ionosphere system, but also for the forcing of climate. Numerous studies have shown that the salient features of the solar spectral variability can be reconstructed from the evolution of the photospheric magnetic field.
We make an empirical study on how the irradiance in different spectral regions is related to characteristic classes of magnetic structures based on their size and intensity.
In particular we build proxy time series based on magnetograms that best describe UV and EUV variations.
These proxies are used to model solar spectral irradiance variability and allow to make a reconstruction when no observations are available. Employing of synoptic map images allows us to forecast solar spectral irradiance with a horizon of 1 month.

7   11:45   The PREMOS/PICARD Radiometer: An Overview after 3 Years of Observations
Cessateur, Gaël; Shapiro, Alexander; Schmutz, Werner

Total and Spectral Solar Irradiance are key input parameters to atmospheric/oceanic and space weather models. We present here spectral solar irradiance data from the radiometer PREMOS onboard the PICARD satellite for three years. This instrument covers the solar spectrum from the Ultraviolet to near-infrared, and provide valuable information, which helps to constrain theoretical models.

An overview of the results involving PREMOS observations will be presentedincluding analysis of several solar eclipses and variability modeling. The analysis of eclipse observations allows us to accurately retrieve the center-to-limb variations (CLV) of the solar brightness. We use radiative transfer code COSI to model the variability of the irradiance, assuming that the latter is determined by the evolution of the solar surface magnetic field as seen with SDO/HMI data. A direct comparison shows a very good correlation for mostof channels from PREMOS.

8   12:05   The Comparison of Solar and Stellar Variabilities
Shapiro, Alexander; Schmutz, Werner; Cessateur, Gael; Rozanov, Eugene

Monitoring of the photometric and chromospheric HK emission data series of stars similar to the Sun in average activity level and age showed that there is a correlation between the stellar average chromospheric activity level and photometric variability. We aim to understand whether the Sun obeys the empirical relationship prompted by the stellar data and to identify possible reasons for the Sun to be currently outside of this relationship. Our analysis suggests that although present solar variability is significantly smaller than indicated by the stellar data, the temporal mean solar variability might be in agreement with the stellar data.


Seq   Title
1   Modeling of Electron Production Rate Profiles in the Ionosphere during GLE 70 on 13 December 2006 using Various Models
Mishev, Alexander1; Velinov, Peter2; Asenovski, Simeon2; Mateev, Lachezar2
1SGO(Oulu unit) University of Oulu, FINLAND;

The ground level enhancement (GLE) of cosmic rays (CRs) on December of 13, 2006 is one of the biggest GLEs in 23rd cycle (behind GLE 69 from 20 January 2005 only) in minimum phase of solar cycle. The greatest maximum was recorded at Oulu Neutron Monitor Station (92.1 %), i.e. the maximum of GLE70 was recorded at sub-polar stations, which shows that the anisotropy source was located near the equator.
Here we compute in details the ionization effects in the terrestrial middle atmosphere and ionosphere (30-120 km) for various latitudes. The computation of electron production rate profiles q(h) is according the operational model CORIMIA (COsmic Ray Ionization Model for Ionosphere and Atmosphere). This improved CR ionization model is important for investigation of the different space weather effects. The influence of galactic and solar CR is computed with the new version of CORIMIA code, which is with fully operational implementations. The solar CR spectra are taken from recent reconstructions from ground based measurements with neutron monitors. Hence we compute the time evolution of the electron production rates q(h) in the ionosphere and middle atmosphere. The full 24h ionization effect is also determined. Comparison between the effects on GLE 70 (13 December 2006) and the major GLE 69 (20 January 2005) is made. In addition, a comparison between the results obtained by COIIMIA and CORSIKA in the region 30-40 km have been carried out.
The cosmic rays determine to a great extent the chemistry and electrical parameters in the ionosphere and atmosphere. They create ozonosphere and influence actively the stratosphere ozone processes. But the ozonosphere controls the meteorological solar constant and the thermal regime and dynamics of the lower atmosphere, i.e. the weather and climate processes. The CR flux varies during the solar cycle in an opposite face to that of sunspots. This hypothesis of the solar-terrestrial relationships shows the way to a non-contradictory solution of the key problems of the solar-terrestrial influences.

2   H2 Emissions of the Upper Atmosphere of Uranus
Barthelemy, Mathieu1; Lamy, Laurent2; Cessateur, Gael3; Schulik, Mattaus4; Menager, Helene1
3Physikalisch-Meteorilogisches Observatorium Davos / World Radiation Center, SWITZERLAND;
4UJF/CNRS; University of Wurzburg, GERMANY

Recent observations of Uranus allow us to re-detect an auroral emission of Uranus during the progression of an interplanetary shock [1]. However during this campaign some low-resolution observations have been performed with the STIS spectrometer. Our aim is to use the Trans* family code to calculate the intensity of the H2 emission on Uranus.
The Trans* family code have been used to calculate the emission of a large set of planet from the Earth [2] to Jupiter [3] and exoplanets [4]. It is a kinetic transport code, which calculates the effect of primary and secondary electrons in the upper atmosphere of planets especially the ionizations, excitations and thus the spectral lines emissions. By coupling this code to the emission code developed by Menager et al. for the jovian H2 emissions, we are able to calculate these emissions. The comparison with the data has been done along the STIS slit. Depending on the S/N for H2 lines, we integrated on the entire disk. We are able to obtain an evaluation of the electrons spectrum that produces these H2 emissions and to detect the specific H2 emission of an auroral event the 29th october 2011.

[1] Lamy et al. GRL; VOL. 39, L07105, 6 PP., 2012
[2] Lummerzheim, D.; Lilensten, J..Ann Geo, vol. 12, no. 10-11, p. 1039-1051, 1994.
[3] Menager et al. Astronomy and Astrophysics, Volume 509, id.A56, 2010.
[4] Menager et al. Icarus. 2013.

3   Variability of the Atmosphere in Mid-Latitudes
Koucka Knizova, Petra; Mosna, Zbysek; Huth, Radan; Jackova, Katerina

Terrestrial atmosphere displays high variability on wide scales. All atmosphere regions are strongly influenced and consequently modified by the solar activity. Energy input from the Sun (solar flux and IMF) varies significantly in a broad time-scale range from short extreme events (for instance geospheric storms) through regular diurnal and seasonal changes, solar cycles to secular variations of periodic and quasi-periodic character. Monitoring of the atmosphere reflects changes on scales from seconds up to long periods of tens of years or even secular changes. We present temporally and spatially dependent ionospheric response to solar, geomagnetic, and neutral atmosphere effects in midlatitudes.