During 9–10 September 2011 the ACE, Wind, and SOHO spacecraft measured the complex interaction between an interplanetary coronal mass ejection (ICME) and a corotating interaction region (CIR) associated with the heliospheric sector boundary. Except for a few short periods, the suprathermal electrons are unidirectional, suggesting that the ICME magnetic field has opened through interchange reconnection. Signatures of interaction are distributed throughout the event suggesting that the structures have become entangled or embedded. Since the ICME speed is relatively low, the strong forward shock must be caused by the ICME‐CIR interaction. Other interesting features are the upstream heating flux discontinuity, the very high proton density in the frontal boundary of the heliospheric plasma sheet and the forward shock, the significant speed elevation within the sheath, the distortion of Bz in the magnetic cloud, the indistinct location of the stream interface, the unidirectional domination of the suprathermal electrons, and the reverse shock at the CIR rear boundary. There is an unusual delay between the proton density and temperature profiles. Furthermore, large differences in proton speed and forward shock density measured between L1 spacecraft indicate high variation at small spatial scales. A few days earlier, STEREO B recorded the undisturbed CIR, which shows that (i) some general features of the CIR are preserved, (ii) the CIR is compressed by a factor of ∼4 by the ICME, and (iii) a magnetic exhausted region at the front of the CIR is a continuous feature and is not formed due to the ICME interaction.

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The aim of this study is to investigate the response of the Ionospheric E- region critical frequency foE and virtual height h’E parameters to the solar cycle 22 over Baghdad city (latitude 33.3˚N, longitude 44.4˚E). Both parameters display a high relationship with the sunspot relative number within the ascending and descending phases of the solar cycle. The E - region response to the solar activity is obvious around noon, sunrise and sunset times. Moreover, the gap between local mid-afternoon, dawn and sunset values expands as solar activity rises. In the declining phase, there is an aspect that results in a peak of disturbance. This portion may have linked to coronal holes and resulted in high disturbance peak during 1992-1994. The impact of this portion is obvious in raising the values of foE, especially in 1993.

The interaction of interplanetary coronal mass ejections (ICME) with each other and with co-rotating interaction regions (CIR) changes their configuration, dynamics, magnetic field and plasma characteristics and can make space weather forecasting difficult. During the period of March 20-25, 2011, the Solar Terrestrial Relation Observatory (STEREO B) encountered a compound stream containing several interacting structures. Our analysis suggests that the stream consists of two ICMEs followed by an embedded ICME/CIR. The sudden appearance of the third ICME within the fast wind side of the CIR causes the proton temperature(T p ) to drop suddenly to its lowest level in about 1.2 hours, from 3.89 × 10 5 K to 1.07 × 10 4 K (by a factor of ≈36). The fast wind which follows the CIR influences not only the third ICME's temperature but also its proton beta (β p ). In addition, the third ICME impacts the CIR through expansion and deceleration. A forward pressure wave penetrates ICME1. It's source is either the second ICME, the merged third ICME and CIR, or it may be a remnant shock. The compression causes an increase of the T p and β p of the second and part of the first ICME. Despite the signatures of four large-scale interacting structures within the compound stream, it is difficult to reconcile the in-situ sequence with other remote sensing observations of ejecta close to the Sun because of the large system of coronal expanding loops above the active region. Compound streams therefore remain difficult to interpret, and further understanding of the subject will depend on the future study of similar events.