ORCID Profile
0000-0002-4401-0943
Current Organisations
International Space Science Institute
,
University of Orléans
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Publisher: American Astronomical Society
Date: 02-2020
Abstract: We compare magnetic field measurements taken by the FIELDS instrument on board Parker Solar Probe ( PSP ) during its first solar encounter to predictions obtained by potential field source surface (PFSS) modeling. Ballistic propagation is used to connect the spacecraft to the source surface. Despite the simplicity of the model, our results show striking agreement with PSP ’s first observations of the heliospheric magnetic field from ∼0.5 au (107.5 R ⊙ ) down to 0.16 au (35.7 R ⊙ ). Further, we show the robustness of the agreement is improved both by allowing the photospheric input to the model to vary in time, and by advecting the field from PSP down to the PFSS model domain using in situ PSP /Solar Wind Electrons Alphas and Protons measurements of the solar wind speed instead of assuming it to be constant with longitude and latitude. We also explore the source surface height parameter ( R SS ) to the PFSS model, finding that an extraordinarily low source surface height (1.3–1.5 R ⊙ ) predicts observed small-scale polarity inversions, which are otherwise washed out with regular modeling parameters. Finally, we extract field line traces from these models. By overlaying these on extreme ultraviolet images we observe magnetic connectivity to various equatorial and mid-latitude coronal holes, indicating plausible magnetic footpoints and offering context for future discussions of sources of the solar wind measured by PSP .
Publisher: American Geophysical Union (AGU)
Date: 28-08-2012
DOI: 10.1029/2012GL052950
Publisher: Wiley
Date: 13-11-2021
Publisher: Wiley
Date: 17-11-2021
Publisher: Wiley
Date: 06-12-2021
Publisher: Wiley
Date: 24-12-2021
Publisher: American Geophysical Union (AGU)
Date: 02-07-2022
DOI: 10.1029/2021JD036146
Abstract: Since the late 1970s, successive satellite missions have been monitoring the sun's activity and recording the total solar irradiance (TSI). Some of these measurements have lasted for more than a decade. In order to obtain a seamless record whose duration exceeds that of the in idual instruments, the time series have to be merged. Climate models can be better validated using such long TSI time series which can also help to provide stronger constraints on past climate reconstructions (e.g., back to the Maunder minimum). We propose a 3‐step method based on data fusion, including a stochastic noise model to take into account short and long‐term correlations. Compared with previous products scaled at the nominal TSI value of ∼1361 W/m 2 , the difference is below 0.2 W/m 2 in terms of solar minima. Next, we model the frequency spectrum of this 41‐year TSI composite time series with a Generalized Gauss‐Markov model to help describe an observed flattening at high frequencies. It allows us to fit a linear trend into these TSI time series by joint inversion with the stochastic noise model via a maximum‐likelihood estimator. Our results show that the litude of such trend is ∼−0.004 ± 0.004 W/(m 2 yr) for the period 1980–2021. These results are compared with the difference of irradiance values estimated from two consecutive solar minima. We conclude that the trend in these composite time series is mostly an artifact due to the colored noise.
Publisher: American Astronomical Society
Date: 03-02-2020
No related grants have been discovered for Thierry Dudok de Wit.