Sonnenwind und neutrale Atome in der Heliosphäre: Analyse von aktuellen Daten und Vorbereitungen für zukünftige Missionen

Here we will focus on two aspects of the heliosphere, namely the slow solar wind and energetic neutral atoms. While the slow solar wind is well characterized in its parameters, the mechanisms of its origin at the Sun are not well understood. Regarding the energetic neutral atoms neither their characteristics nor their origin is well understood, since there are few direct observations of these particles. In this work on the hand we look at observational data of the slow solar wind and combine this with a model of the coronal magnetic field in order to better understand its origin. On the other hand we prepare future missions for the measurement of the source regions of the slow solar wind and the observation of heliospheric neutral particles. The observational data covered here was taken by the Ulysses and ACE spacecraft and it is combined with a Potential Field Source Surface ( PFSS ) model that gives us the magnetic field line configuration in the corona. From this we draw conclusions about the mechanism that might release the plasma which makes up the slow solar wind. To support the upcoming Solar Orbiter mission we devised a measurement scheme for the Spectral Imaging of the Coronal Environment ( SPICE ) instrument which will enable the remote observation of solar wind plasma at its source location and the in-situ measurement of the very same plasma package with in-situ particle detectors. This kind of observation will hopefully greatly improve our understanding of the formation of slow solar wind. And finally we help prepare the foundation of future missions that measure the neutral component in the heliosphere by establishing a calibration facility for he- liospheric particle detectors. Part of this facility are Faraday cups which measure the particle beams. These Faraday cups have been calibrated for the detection of neutral particles and serve now as reference detectors for future neutral particle detectors.Wir werden uns hier auf den langsamen Sonnenwind und energiereiche neutrale Atome fokusieren. Während der langsame Sonnenwind in seinen Eigenschaften gut charakterisiert ist, ist sein Ursprung auf der Sonne nicht gut verstanden. Im Falle der energiereichen neutralen Atome sind weder ihr genauen Eigenschaften noch ihr Ursprung gut verstanden. In dieser Arbeit werden wir uns zum einen Beobachtungsdaten des langsamen Sonnenwindes anschauen und diese mit einem Modell des koronalen Magnetfelds kombinieren um seinen Ursprung besser zu verstehen. Zum anderen werden wir Vorberei- tungen für zukünfitge Missionen treffen um diesen die Beobachtung der Quellregionen des langsamen Sonnenwindes und energiereicher neutraler Teilchen zu ermöglichen. Die in dieser Arbeit benutzten Beobachtungen wurden von den Sonden Ulysses und ACE aufgenommen und mit einem so genannten Potential Field Source Surface ( PFSS ) Modell verknüpft. Dieses Modell simuliert das Magnetfeld in der Ko- rona. Damit können wir Schlussfolgerungen über die möglichen Mechanismen ziehen, die für die Freisetzung des Plasmas verantwortlich sind, welches den langsamen Sonnenwind ausmacht. Für die geplante Mission Solar Orbiter haben wir ein Messschema für das SPICE Instrument entworfen. Dieses wird es ermöglichen das Sonnenwindplasma an seiner Quellregion auf der Sonne zu beobachten. Das selbe Plasmapacket wird dann ein weiteres mal in-situ mit einem Partikeldetektor auf Solar Orbiter detektiert. Im letzten Teil der Arbeit haben wir geholfen ein Fundament für zukünftige Missio- nen zu legen, die die neutrale Teilchenkomponente in der Heliosphäre messen werden, indem der Aufbau einer Kalibrationseinrichtung für heliosphärische Teilchendetektoren unterstüzt wurde. Teil dieser Einrichtung sind Faraday Cups, die dafür genutzt werden die erzeugten Teilchenstrahlen zu messen. Die Faraday Cups wurden in dieser Arbeit für die Detektion von neutralen Teilchen kalibriert und dienen nun als Referenzdetektoren

Evolution of an equatorial coronal hole structure and the released coronal hole wind stream: Carrington rotations 2039 to 2050

The Sun is a highly dynamic environment that exhibits dynamic behavior on many different timescales. In particular, coronal holes exhibit temporal and spatial variability. Signatures of these coronal dynamics are inherited by the coronal hole wind streams that originate in these regions and can effect the Earth's magnetosphere. Both the cause of the observed variabilities and how these translate to fluctuations in the in situ observed solar wind is not yet fully understood. During solar activity minimum the structure of the magnetic field typically remains stable over several Carrington rotations (CRs). But how stable is the solar magnetic field? Here, we address this question by analyzing the evolution of a coronal hole structure and the corresponding coronal hole wind stream emitted from this source region over 12 consecutive CRs in 2006. To this end, we link in situ observations of Solar Wind Ion Composition Spectrometer (SWICS) onboard the Advanced Composition Explorer (ACE) with synoptic maps of Michelson Doppler imager (MDI) on the Solar and Heliospheric Observatory (SOHO) at the photospheric level through a combination of ballistic back-mapping and a potential field source surface (PFSS) approach. Together, these track the evolution of the open field line region that is identified as the source region of a recurring coronal hole wind stream. We find that the shape of the open field line region and to some extent also the solar wind properties are influenced by surrounding more dynamic closed loop regions. We show that the freeze-in order can change within a coronal hole wind stream on small timescales and illustrate a mechanism that can cause changes in the freeze-in order. The inferred minimal temperature profile is variable even within coronal hole wind and is in particular most variable in the outer corona

Origin of the solar wind: A novel approach to link in situ and remote observations

Context. During the last decades great progress has been achieved in understanding the properties and the origin of the solar wind. While the sources for the fast solar wind are well understood, the sources for the slow solar wind remain elusive. Aims. The upcoming Solar Orbiter mission aims to improve our understanding of the sources of the solar wind by establishing the link between in situ and remote sensing observations. In this paper we aim to address the problem of linking in situ and remote observations in general and in particular with respect to ESA’s Solar Orbiter mission. Methods. We have used a combination of ballistic back mapping and a potential field source surface model to identify the solar wind source regions at the Sun. As an input we use in situ measurements from the Advanced Composition Explorer and magnetograms obtained from the Michelson Doppler Interferometer on board the Solar Heliospheric Observatory. For the first time we have accounted for the travel time of the solar wind above and also below the source surface. Results. We find that a prediction scheme for the pointing of any remote sensing instrumentation is required to capture a source region not only in space but also in time. An ideal remote-sensing instrument would cover up to ≈50% of all source regions at the right time. In the case of the Spectral Imaging of the Coronal Environment instrument on Solar Orbiter we find that ≈25% of all source regions would be covered. Conclusions. To successfully establish a link between in situ and remote observations the effects of the travel time of the solar wind as well as the magnetic displacement inside the corona cannot be neglected. The predictions needed cannot be based solely on a model, nor on observations alone, only the combination of both is sufficient

Observations of high and low Fe charge states in individual solar wind streams with coronal-hole origin

Context. The solar wind originating from coronal holes is comparatively well-understood and is characterized by lower densities and average charge states compared to the so-called slow solar wind. Except for wave perturbations, the average properties of the coronal-hole solar wind are passably constant. Aims. In this case study, we focus on observations of the Solar Wind Ion Composition Spectrometer (SWICS) on the Advanced Composition Explorer (ACE) of individual streams of coronal-hole solar wind that illustrate that although the O and C charge states are low in coronal-hole wind, the Fe charge distribution is more variable. In particular, we illustrate that the Fe charge states in coronal-hole solar wind are frequently as high as in slow solar wind. Methods. We selected individual coronal-hole solar wind streams based on their collisional age as well as their respective O and C charge states and analyzed their Fe charge-state distributions. Additionally, with a combination of simple ballistic back-mapping and the potential field source surface model, transitions between streams with high and low Fe charge states were mapped back to the photosphere. The relative frequency of high and low Fe charge-state streams is compared for the years 2004 and 2006. Results. We found several otherwise typical coronal-hole streams that include Fe charge states either as high as or lower than in slow solar wind. Eight such transitions in 2006 were mapped back to equatorial coronal holes that were either isolated or connected to the northern coronal-hole. Attempts to identify coronal structures associated with the transitions were so far inconclusive