Extreme Ultraviolet Solar Irradiance during the rising phase of solar cycle 24 observed by PROBA2/LYRA

TL;DR

This paper presents measurements of the extreme ultraviolet solar irradiance during solar cycle 24's rising phase using PROBA2/LYRA, highlighting an increase in EUV irradiance consistent with SDO/EVE data.

Contribution

It details the methodology for deriving long-term EUV irradiance time series from LYRA data and compares it with EVE observations, providing new insights into solar cycle variations.

Findings

EUV irradiance increased by a factor of 2 since last solar minimum.

LYRA data shows good agreement with SDO/EVE measurements.

Methodology for long-term EUV irradiance retrieval is established.

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 space- craft, PROBA2 (Project for On-Board 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 SDO/EVE. We find that the solar EUV irradi- ance has increased by a factor 2 since the last solar minimum (between solar cycles 23 and 24), which agrees reasonably well with the EVE observations.