Adalbert Ding

Technische Universität Berlin, Istitut für Optik und Atomare Phzsik, Emeritus

Followers

34,665

Following

Co-authors

Public Views

InterestsView All (10)

Uploads

Papers by Adalbert Ding

The Need for a New Generation of Space-based Visible and Near-IR Emission Line Observations of the Corona

arXiv (Cornell University), Feb 22, 2023

Download

The Temperature of the Corona as Derived from Total Solar Eclipse Observations

On the Detection of Fast Moving H, He and Neutral Atoms in the Solar Corona During the Total Solar Eclipses of 2015 and 2017

Electron Energy-Loss Spectroscopy of Free Fullerenes

Springer Series in Solid-State Sciences, 1993

Pure samples of C60 and C70 were analyzed using electron energy loss spectroscopy (EELS). By vary... more Pure samples of C60 and C70 were analyzed using electron energy loss spectroscopy (EELS). By varying the energy of the primary electrons optically allowed transitions could be distinguished from optically forbidden ones and from collective excitations. The collective excitation lines of C60 could be assigned to dipole and monopole excitations. The EEL-spectra of C70 exhibited a splitting of the plasmon excitation which is attributed to the non-sperical shape of the C70 molecule.

Photoionization Dynamics of C60

Springer Series in Solid-State Sciences, 1993

Photoionization of C60 by means of synchrotron radiation is reported. The present investigation c... more Photoionization of C60 by means of synchrotron radiation is reported. The present investigation covers an energy range of 15-120 eV. The findings are compared with other recent reports focusing on the ionization and fragmentation behaviour of C60 as a result of certain energy transfer processes to the cluster. The actual ionization mechanism, the temperature dependence on the ion yield curve and the fragmentation behaviour of ionic C60 are discussed.

Fragmentation spectroscopy of heterogeneous clusters

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1988

Photoionisation experiments were performed with heterogeneous Ar-Xe-clusters produced by superson... more Photoionisation experiments were performed with heterogeneous Ar-Xe-clusters produced by supersonic expansion of argon gas with small quantities of xenon added to it. A threshold-electron photoionisation (TEPICO) technique was used to obtain time of flight cluster mass spectra. These mass spectra show particularly strong intensities for Ar12Xe + and ArlsXe + which are attributed to the extraordinary stabilities of these cluster ions. Maxima in the ionic size distribution around ArTXe + are related to a particular abundance of neutral Ar12Xe which is fragmented after ionization. These stabilities are explained in terms of geometries consisting of a central Xe atom or ion surrounded by shells of Ar atoms. Filled shells exhibit particular strong bonding because these exhibit the largest number of atom-atom bonds. This conclusion is supported by simple theoretical calculations. The ionization process is discussed in terms of two direct and one indirect ionization channels the latter one proceeding via an intermediate electronic excitation of the Ar component in the neutral cluster.

Download

The dynamics of the double photoionization of C60

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1993

The photoionization dynamics of C60 has been studied by means of synchrotron radiation. The findi... more The photoionization dynamics of C60 has been studied by means of synchrotron radiation. The findings for single-photon ionization covering an energy range of 15 -120 eV are presented and contrasted with other experiments recently performed to elucidate the fragmentation and the ionization behaviour of fullerences as a result of relatively high energy impact. In this context, special emphasis is paid

Coordinated Visible, EUV and White Light Observations of the Extended Corona During the 2010 July 11 Total Solar Eclipse

ABSTRACT Eclipse observations of coronal forbidden lines emitted by highly ionized elements are u... more ABSTRACT Eclipse observations of coronal forbidden lines emitted by highly ionized elements are unique as they extend the field of view of space-borne high-resolution EUV spectrometers and narrow-band EUV imagers up to several solar radii. Furthermore, they combine in one single dataset the two main features of space-borne instrumentation: high spatial resolution 2D images of the solar corona and full temperature resolution and diagnostic potential allowed by monochromatic imaging of individual spectral lines. The limitation of the published eclipse results, however, has been the absence of an absolute calibration. In the present work, we combine the 2010 July 11 eclipse observations with simultaneous observations carried out with the Hinode/EIS instrument. Such a combination allows us to calibrate the eclipse images and to use them to carry out detailed plasma diagnostics in the extended corona out to a few solar radii using a variety of techniques.

On the Constancy of the Electron Temperature in the Expanding Corona Throughout Solar Cycle 23

The Astrophysical Journal, 2010

A recent analysis of Fe emission lines observed during the total solar eclipses of 2006 March 29 ... more A recent analysis of Fe emission lines observed during the total solar eclipses of 2006 March 29 and 2008 August 1 established the first empirical link between the electron temperature in the expanding corona and Fe charge states measured in interplanetary space. In this Letter, we use this link to infer this temperature throughout solar cycle 23 from in situ

The quiet yet turbulent solar corona during the 2 July 2019 total solar eclipse

Observations of the Dynamics and Thermodynamics of the Corona during the 21 August 2017 Total Solar Eclipse

CME-induced Thermodynamic Changes in the Corona as Inferred from Fe xi and Fe xiv Emission Observations during the 2017 August 21 Total Solar Eclipse

The Astrophysical Journal

We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME)... more We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 R. Measurements of the Fe xi (789.2 nm) and Fe xiv (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse. Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe xi and Fe xiv emission relative to continuum scattering, as well as the relative abundance of Fe 10+ and Fe 13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is 1.1 − 1.2 × 10 6 K in coronal holes and 1.2 − 1.4 × 10 6 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength total solar eclipse observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 R .

Download

Imaging comet ISON C/2012 S1 in the inner corona at perihelion

Much anticipation and speculation were building around comet ISON, or

Download

– 1 – Exploring the Physics of the Corona with Total Solar Eclipse Observations

This white paper is a call for a concerted effort to support total solar eclipse observations ove... more This white paper is a call for a concerted effort to support total solar eclipse observations over the next decade, in particular for the 21 August 2017 eclipse which will traverse the US continent. With the recent advances in image processing techniques and detector technology, the time is ripe to capitalize on the unique diagnostic tools available in the visible and near infrared wavelength range to explore the physics of the corona. The advantage of coronal emission lines in this wavelength range, over their extreme ultraviolet counterparts, is (1) the significant radiative component in their excitation process (in addition to the colli-sional excitation), which allows for observations out to a few solar radii, (2) the higher spectral selectivity available for imaging, giving well-defined temperature responses for each bandpass (one line as opposed to many), and (3) the capability of polarization measurements in a number of spectral lines. Consequently, the evolution of the therm...

Download

Unique Insights into the Origin and Expansion of Coronal Structures from Total Solar Eclipse Observations

The Unique Scientific Assets of Multi-Wavelength Total Solar Eclipse Observations

Dynamics and Thermodynamics of the Solar Corona as Inferred from Total Solar Eclipse Observations

太陽光直接励起ND:YAGレーザ【JST・京大機械翻訳】

Identifying the Coronal Source Regions of Solar Wind Streams from Total Solar Eclipse Observations and in situ Measurements Extending over a Solar Cycle

The Astrophysical Journal Letters

This Letter capitalizes on a unique set of total solar eclipse observations, acquired between 200... more This Letter capitalizes on a unique set of total solar eclipse observations, acquired between 2006 and 2020, in white light, Fe xi 789.2 nm (T fexi = 1.2 ± 0.1 MK) and Fe xiv 530.3 nm (T fexiv = 1.8 ± 0.1 MK) emission, complemented by in situ Fe charge state and proton speed measurements from ACE/SWEPAM-SWICS, to identify the source regions of different solar wind streams. The eclipse observations reveal the ubiquity of open structures, invariably associated with Fe xi emission from Fe 10+ , hence a constant electron temperature, T c = T fexi in the expanding corona. The in situ Fe charge states are found to cluster around Fe 10+ , independently of the 300 to 700 km s −1 stream speeds, referred to as the continual solar wind. Fe 10+ thus yields the fiducial link between the continual solar wind and its T fexi sources at the Sun. While the spatial distribution of Fe xiv emission, from Fe 13+ , associated with streamers, changes throughout the solar cycle, the sporadic appearance of charge states > Fe 11+ , in situ, exhibits no cycle dependence regardless of speed. These latter streams are conjectured to be released from hot coronal plasmas at temperatures ≥ T fexiv within the bulge of streamers and from active regions, driven by the dynamic behavior of prominences magnetically linked to them. The discovery of continual streams of slow, intermediate and fast solar wind, characterized by the same T fexi in the expanding corona, places new constraints on the physical processes shaping the solar wind.

Download

The First Empirical Determination of the Fe10+ and Fe13+ Freeze-in Distances in the Solar Corona

The Astrophysical Journal

Heavy ions are markers of the physical processes responsible for the density and temperature dist... more Heavy ions are markers of the physical processes responsible for the density and temperature distribution throughout the fine-scale magnetic structures that define the shape of the solar corona. One of their properties, whose empirical determination has remained elusive, is the "freeze-in" distance (R f) where they reach fixed ionization states that are adhered to during their expansion with the solar wind. We present the first empirical inference of R f for Fe 10 + and Fe 13 + derived from multi-wavelength imaging observations of the corresponding Fe XI (Fe 10 +) 789.2 nm and Fe XIV (Fe 13 +) 530.3 nm emission acquired during the 2015 March 20 total solar eclipse. We find that the two ions freeze-in at different heliocentric distances. In polar coronal holes (CHs) R f is around 1.45 R e for Fe 10 + and below 1.25 R e for Fe 13 +. Along open field lines in streamer regions, R f ranges from 1.4 to 2 R e for Fe 10 + and from 1.5 to 2.2 R e for Fe 13 +. These first empirical R f values: (1) reflect the differing plasma parameters between CHs and streamers and structures within them, including prominences and coronal mass ejections; (2) are well below the currently quoted values derived from empirical model studies; and (3) place doubt on the reliability of plasma diagnostics based on the assumption of ionization equilibrium beyond 1.2 R e .

Download

Adalbert Ding

Uploads

Papers by Adalbert Ding

Log In