Hydrogen permitted lines in the first near-IR spectra of Th 28 microjet: accretion or ejection tracers?

We report the first near-infrared detection of the bipolar microjet from TTauri star ThA 15-28 (aka Th 28). Spectra were obtained with VLT/ISAAC for the slit both perpendicular and parallel to the flow to examine jet kinematics and gas physics within the first arcsecond from the star. The jet was successfully detected in both molecular and atomic lines. The H_2 component was found to be entirely blueshifted around the base of the bipolar jet. It shows that only the blue lobe is emitting in H_2 while light is scattered in the direction of the red lobe, highlighting an asymmetric extinction and/or excitation between the two lobes. Consistent with this view, the red lobe is brighter in all atomic lines. Interestingly, the jet was detected not only in [Fe II], but also in Br gamma and Pa beta lines. Though considered tracers mainly of accretion, we find that these high excitation hydrogen permitted lines trace the jet as far as 150 AU from the star. This is confirmed in a number of ways: the presence of the [Fe II] 2.13 micron line which is of similarly high excitation; H I velocities which match the jet [Fe II] velocities in both the blue and red lobe; and high electron density close to the source of >6x10^4 cm^-3 derived from the [Fe II] 1.64,1.60 micron ratio. These near-infrared data complement HST/STIS optical and near-ultraviolet data for the same target which were used in a jet rotation study, although no rotation signature could be identified here due to insufficient angular resolution. The unpublished HST/STIS H alpha emission is included here along side the other H I lines. Identifying Br gamma and Pa beta as tracers of ejection is significant because of the importance of finding strong near-infrared probes close to the star, where forbidden lines are quenched, which will help understand accretion-ejection when observed with high spatial resolution instruments such as VLTI/AMBER.Comment: 18 pages, 26 figures, Accepted by Ap

T Tauri Jet Physics Resolved Near The Launching Region with the Hubble Space Telescope

We present an analysis of the gas physics at the base of jets from five T Tauri stars based on high angular resolution optical spectra, using the Hubble Space Telescope Imaging Spectrograph (HST/STIS). The spectra refer to a region within 100 AU of the star, i.e. where the collimation of the jet has just taken place. We form PV images of the line ratios to get a global picture of the flow excitation. We then apply a specialised diagnostic technique to find the electron density, ionisation fraction, electron temperature and total density. Our results are in the form of PV maps of the obtained quantities, in which the gas behaviour is resolved as a function of both radial velocity and distance from the jet axis. They highlight a number of interesting physical features of the jet collimation region, including regions of extremely high density, asymmetries with respect to the axis, and possible shock signatures. Finally, we estimate the jet mass and angular momentum outflow rates, both of which are fundamental parameters in constraining models of accretion/ejection structures, particularily if the parameters can be determined close to the jet footpoint. Comparing mass flow rates for cases where the latter is available in the literature (i.e. DG Tau, RW Aur and CW Tau) reveals a mass ejection-to-accretion ratio of 0.01 - 0.07. Finally, where possible (i.e. DG Tau and CW Tau), both mass and angular momentum outflow rates have been resolved into higher and lower velocity jet material. For the clearer case of DG Tau, this revealed that the more collimated higher velocity component plays a dominant role in mass and angular momentum transport.Comment: 33 pages, 16 figures, accepted by Ap

ALMA observations of polarized emission toward the CW Tau and DG Tau protoplanetary disks: constraints on dust grain growth and settling

We present polarimetric data of CW Tau and DG Tau, two well-known Class II disk/jet systems, obtained with the Atacama Large Millimeter/submillimeter Array at 870 $\mu$m and 0."2 average resolution. In CW Tau, the total and polarized emission are both smooth and symmetric, with polarization angles almost parallel to the minor axis of the projected disk. In contrast, DG Tau displays a structured polarized emission, with an elongated brighter region in the disk's near side and a belt-like feature beyond about 0."3 from the source. At the same time the total intensity is spatially smooth, with no features. The polarization pattern, almost parallel to the minor axis in the inner region, becomes azimuthal in the outer belt, possibly because of a drop in optical depth. The polarization fraction has average values of 1.2% in CW Tau and 0.4% in DG Tau. Our results are consistent with polarization from self-scattering of the dust thermal emission. Under this hypothesis, the maximum size of the grains contributing to polarization is in the range 100 - 150 $\mu$m for CW Tau and 50 - 70 $\mu$m for DG Tau. The polarization maps combined with dust opacity estimates indicate that these grains are distributed in a geometrically thin layer in CW Tau, representing a settling in the disk midplane. Meanwhile, such settling is not yet apparent for DG Tau. These results advocate polarization studies as a fundamental complement to total emission observations, in investigations of the structure and the evolution of protoplanetary disks.Comment: 8 pages, 5 figures. Accepted for publication in ApJ Letter

MSFC/EV44 Natural Environment Capabilities

The Natural Environments Branch at Marshall Space Flight Center is an integral part of many NASA satellite and launch vehicle programs, providing analyses of the space and terrestrial environments that are used for program development efforts, operational support, and anomaly investigations. These capabilities include model development, instrument build and testing, analysis of space and terrestrial related data, spacecraft charging anomaly investigations, surface and internal charging modeling, space environment definition, and radiation assessments for electronic parts. All aspects of space and terrestrial design are implemented with the goal of devising missions that are successful from launch to operations in the space environment of LEO, polar, GEO, and interplanetary orbits

Climatology of Deep O+ Dropouts in the Night-Time F-Region in Solar Minimum Measured by a Langmuir Probe Onboard the International Space Station

The Floating Potential Measurement Unit (FPMU) onboard the International Space Station includes a Wide sweeping Langmuir Probe (WLP) that has been operating in the F-region of the ionosphere at ∼400 km since 2006. While traditional Langmuir probe estimates include critical plasma parameters like electron density and temperature, we have also extracted the O+ percentage from the total ion constituents. This O+ composition dataset from the recent minimum in the Solar Cycle 24 reveals orbits with dropouts in O+ to below 80% of the total background ion density at ISS orbital altitudes. The observed O+ percentages during these dropouts are much lower than the values predicted by the International Reference Ionosphere 2016 (IRI2016) empirical model. In this paper, we present the climatology of these O+ dropouts with their dependency on season, local time and geographical location. The results show that the lowered O+ percentages are more significant in the winter hemispheres and are routinely observed for orbits in the pre-sunrise periods. The patterns in O+ dropouts can be explained in part from the lowering of the O+/H+ transition height during solar minimum along with patterns in neutral wind variation

In-situ Observations of the Ionospheric F2-Region from the International Space Station

The International Space Station orbit provides an ideal platform for in-situ studies of space weather effects on the mid and low latitude F-2 region ionosphere. The Floating Potential Measurement Unit (FPMU) operating on the ISS since Aug 2006, is a suite of plasma instruments: a Floating Potential Probe (FPP), a Plasma Impedance Probe (PIP), a Wide-sweep Langmuir Probe (WLP), and a Narrow-sweep Langmuir Probe (NLP). This instrument package provides a new opportunity for collaborative multi-instrument studies of the F-region ionosphere during both quiet and disturbed periods. This presentation first describes the operational parameters for each of the FPMU probes and shows examples of an intra-instrument validation. We then show comparisons with the plasma density and temperature measurements derived from the TIMED GUVI ultraviolet imager, the Millstone Hill ground based incoherent scatter radar, and DIAS digisondes, Finally we show one of several observations of night-time equatorial density holes demonstrating the capabilities of the probes for monitoring mid and low latitude plasma processes

Community-University Partnerships: Achieving continuity in the face of change

A challenge that community-university partnerships everywhere will face is how to maintain continuity in the face of change. The problems besetting communities continually shift and the goals of the university partners often fluctuate. This article describes a decade-long strategy one university has successfully used to address this problem. Over the past ten years, a community-university partnership at the University of Massachusetts Lowell has used summer content funding to respond creativity to shifting priorities. Each summer a research-action project is developed that targets a different content issue that has emerged with unexpected urgency. Teams of graduate students and high school students are charged with investigating this issue under the auspices of the partnership. These highly varied topics have included immigrant businesses, youth asset mapping, women owned businesses, the housing crisis, social program cutbacks, sustainability, and economic development and the arts. Despite their obvious differences, these topics share underlying features that further partnership commitment and continuity. Each has an urgency: the information is needed quickly, often because some immediate policy change is under consideration. Each topic has the advantage of drawing on multiple domains: the topics are inherently interdisciplinary and because they do not “belong” to any single field, they lend themselves to disciplines pooling their efforts to achieve greater understanding. Each also has high visibility: their salience has meant that people were often willing to devote scarce resources to the issues and also that media attention could easily be gained to highlight the advantages of students, partners, and the university working together. And the topics themselves are generative: they have the potential to contribute in many different ways to teaching, research, and outreach. This paper ends with a broader consideration of how partnerships can implement this model for establishing continuity in the face of rapidly shifting priorities and needs

Community-University Partnerships: Achieving continuity in the face of change

A challenge most community-university partnerships will face after having established themselves is how to maintain continuity in the face of change. The problems besetting communities continually shift as new issues bubble up. Similarly, the goals of the university partners often fluctuate. And the partners themselves shift: people working in non-government organizations often move in and out of positions and university partners may change with tenure or shifts in university priorities. In light of all of this flux, can stable community-university partnerships be built and, if so, how

The near-UV: the true window on jet rotation

High resolution observations of jet rotation in newly forming stars have the potential to support theories of magneto-centrifugal jet launching. We report a detection of a radial velocity difference across the blue-shifted jet from RY Tau, the direction of which matches the CO disk rotation sense. Now, in 3 of 3 cases, the sense of the near-UV jet gradient matches the disk rotation sense, implying that we are indeed observing jet rotation. It seems the jet core, probed at near-UV wavelengths, is protected by the outer jet layers from kinematic contaminations, and thus represents the only true window on jet rotation