Extreme ultraviolet solar irradiance during the rising phase of solar cycle 24 observed by PROBA2/LYRA

¹ Royal Observatory of Belgium/Solar Terrestrial Center of Excellence, av. circulaire 3, 1180 Brussels, Belgium
² LPC2E, UMR 6115 CNRS and University of Orléans, 3a av. de la recherche scientifique, 45071 Orléans, France
³ Royal Observatory of Belgium/Solar Influence Data Analysis Center, av. circulaire 3, 1180 Brussels, Belgium
⁴ ESA Research and Scientific Support Department, ESTEC, NL-2200 AG Noordwijk, The Netherlands
⁵ Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC), Dorfstrasse 33, 7260 Davos Dorf, Switzerland

^* corresponding author: e-mail: matthieu.kretzschmar@cnrs-orleans.fr

Received: 26 March 2012
Accepted: 27 July 2012

Abstract

The Large-Yield Radiometer (LYRA) is a radiometer that has monitored the solar irradiance at high cadence and in four pass bands since January 2010. Both the instrument and its spacecraft, PROBA2 (Project for OnBoard Autonomy), have several innovative features for space instrumentation, which makes the data reduction necessary to retrieve the long-term variations of solar irradiance more complex than for a fully optimized solar physics mission. In this paper, we describe how we compute the long-term time series of the two extreme ultraviolet irradiance channels of LYRA and compare the results with those of SDO/EVE. We find that the solar EUV irradiance has increased by a factor of 2 since the last solar minimum (between solar cycles 23 and 24), which agrees reasonably well with the EVE observations.