Richard Eastes

Modeling the N2 Lyman‐Birge‐Hopfield bands in the dayglow: Including radiative and collisional cascading between the singlet states

A new model for the daytime airglow emissions from the N2 Lyman-Birge-Hopfield (LBH) bands (a1Πg–X1Σ+g) in the Earths atmosphere is presented. This model gives good agreement, which other first principles models have been unable to obtain, with dayglow observations reporting increased vibrational populations, relative to direct excitation, for v ≤1 of the N2 a1Πg state. The ability of the model to match the observations is due to the inclusion of radiative and collisional cascading between the singlet states. Such cascading was not included in previous first principles dayglow calculations for the singlet states. Not only does cascading improve the fit between the observed and modeled relative vibrational populations, it also increases the total emission from the LBH bands by a factor of ∼1.6 due to the transfer of excitation from the a′ and w states to the a state, resulting in significantly greater emission than predicted by earlier models using the same excitation cross section for the a state. Such an increase in the total emission from the LBH bands is consistent with recent work by Budzien et al. [1994] and Link et al. [1994]. The coupling between the singlet states will have a significant impact on the interpretation of the LBH band emissions from the Earths atmosphere.

Multifractal analysis of geomagnetic storm and solar flare indices and their class dependence

The multifractal properties of two indices of geomagnetic activity, D st (representative of low latitudes) and a p (representative of the global geomagnetic activity), with the solar X-ray brightness, X l , during the period from 1 March 1995 to 17 June 2003 are examined using multifractal detrended fluctuation analysis (MF-DFA). The h(q) curves of D st and a p in the MF-DFA are similar to each other, but they are different from that of X l , indicating that the scaling properties of X l are different from those of D st and a p . Hence, one should not predict the magnitude of magnetic storms directly from solar X-ray observations. However, a strong relationship exists between the classes of the solar X-ray irradiance (the classes being chosen to separate solar flares of class X-M, class C, and class B or less, including no flares) in hourly measurements and the geomagnetic disturbances (large to moderate, small, or quiet) seen in D st and a p during the active period. Each time series was converted into a symbolic sequence using three classes. The frequency, yielding the measure representations, of the substrings in the symbolic sequences then characterizes the pattern of space weather events. Using the MF-DFA method and traditional multifractal analysis, we calculate the h(q), D(q), and τ (q) curves of the measure representations. The τ (q) curves indicate that the measure representations of these three indices are multifractal. On the basis of this three-class clustering, we find that the h(q), D(q), and τ (q) curves of the measure representations of these three indices are similar to each other for positive values of q. Hence, a positive flare storm class dependence is reflected in the scaling exponents h(q) in the MF-DFA and the multifractal exponents D(q) and τ (q). This finding indicates that the use of the solar flare classes could improve the prediction of the D st classes.

Underlying scaling relationships between solar activity and geomagnetic activity revealed by multifractal analyses

Free to read This paper identifies some scaling relationships between solar activity and geomagnetic activity. We examine the scaling properties of hourly data for two geomagnetic indices (ap and AE), two solar indices (solar X-rays Xl and solar flux F10.7), and two inner heliospheric indices (ion density Ni and flow speed Vs) over the period 1995–2001 by the universal multifractal approach and the traditional multifractal analysis. We found that the universal multifractal model (UMM) provides a good fit to the empirical K(q) and τ(q) curves of these time series. The estimated values of the Levy index α in the UMM indicate that multifractality exists in the time series for ap, AE, Xl, and Ni, while those for F10.7 and Vs are monofractal. The estimated values of the nonconservation parameter H of this model confirm that these time series are conservative which indicate that the mean value of the process is constant for varying resolution. Additionally, the multifractal K(q) and τ(q) curves, and the estimated values of the sparseness parameter C1 of the UMM indicate that there are three pairs of indices displaying similar scaling properties, namely ap and Xl, AE and Ni, and F10.7 and Vs. The similarity in the scaling properties of pairs (ap,Xl) and (AE,Ni) suggests that ap and Xl, AE and Ni are better correlated—in terms of scaling—than previous thought, respectively. But our results still cannot be used to advance forecasting of ap and AE by Xl and Ni, respectively, due to some reasons

Scanless ultraviolet remote sensor for limb profile measurements from low earth orbit

Ultraviolet (UV) observations of the Earths upper atmosphere are essential for meeting operational requirements for space weather specification and prediction. Such observations provide valuable information about neutral and ion density variations. Current operational sensors measure the limb profiles by mechanically scanning the field of view across the limb. This mechanical scan mechanism requires significant power and can fail, and the high counting rates during observations near the peak of the limb profile require high-speed detectors to accommodate the counting rates when using the high-sensitivity sensors. This paper describes an instrument that can provide limb observations of the UV airglow by aligning the slit perpendicular to the limb. To measure the limb profile without scanning requires a combination of wide field of view and high spatial resolution that previous instruments have been unable to provide. This approach would require significantly less resources (power, weight, etc.) than current sensors, while providing similar performance. A preliminary scattering analysis of the instrument is also included.

Scanless ultraviolet remote sensor for limb profile measurements from low Earth orbit

Ultraviolet (UV) observations are essential for meeting operational requirements for space weather specification. Such observations provide valuable information about neutral and ion density variations in the Earth’s upper atmosphere. However, the resources required to support the necessary ultraviolet sensors are significant. Current operational sensors measure the limb profiles by mechanically scanning the field-of-view across the limb. This mechanical scan mechanism requires significant power, has a potential for failure, and the high counting rates during observations near the peak of the limb profile require high speed detectors to accommodate the counting rates when using the high sensitivity sensors. Also, the attitude information and stability needed for accurate limb profiles are more difficult on smaller spacecraft and require considerable resources. This paper describes an instrument that can provide limb observations of the UV airglow by aligning the slit perpendicular to the limb. To measure the limb profile without scanning requires a combination of wide field-of-view and high spatial resolution which previous instruments have been unable to provide. This approach would require significantly less resources (power, weight, etc.) than current sensors, while providing similar performance.